Research Groups
Twisted magnetic topological insulator: When momentum-space topology meets real-space topology?
Prof. G. Chen's research
Prof. G. Chen's research

AoE & CRF & RIF Awards in HKU Physics

Area of Excellence

on Meta-optics, Meta-acoustics and Meta-devices

Project Coordinator: D.P. Tsai (PolyU)
: C.T. Chan (HKUST), P. Sheng (HKUST), S. Zhang (HKU), J.T.H. Li (HKUST), J. Zhu (PolyU), K.H. Fung (PolyU)
Co-Is: J. Pendry (Imperial College London), T. Tanaka (RIKEN)
Collaborators: J. Yao (UC Berkerly, USA), X. Zhang (HKU), M. Fink (ESCPI Paris Tech, France)

We aim at developing novel meta-materials and meta-devices that can control and manipulate electromagnetic and acoustic waves for improving the quality of human daily life. Metamaterials and meta-devices take advantages of the localized and non-localized resonances of artificial structures in which the response of the electrons, phonons, plasmons, and excitons are strongly modified to give novel properties and functionalities which are not found in nature. Our project will cover the design, numerical simulation, advanced manufacturing, characterizations and measurements of these materials for various applications including environment, biomedical, imaging and sensing, and information security. We expect that this AoE project will generate a new platform for knowledge-based intelligent artificial materials and devices which are low energy consumption (“green”) and compatible with advanced manufacture 4.0 in micro- and nano-electronics industrial techniques for wearable or portable innovation. We trust that local impact and global excellence will be fully demonstrated by the results of this AoE project. The existing world-renowned research strength of different local universities will be assembled and propelled to a higher level by this strategic project. Local young talents will be incubated, and global talents will be attracted to Hong Kong. The intellectual properties and innovations of meta-devices in this project will be transferred to the local industries and business sectors. The upstream knowledge and intellectual properties can strategically transform and upgrade Hong Kong’s high-technical industries and business sectors. Hong Kong is currently unique in having a critical mass of metamaterial scientists, capable of making fundamental discoveries and deliver to the real world applications and benefiting business and industries in the Greater Bay Area.


Area of Excellence

on 2D Materials Research: Fundamentals Towards Emerging Technologies

Project Coordinator: W. Yao (HKU)
Deputy PC & Co-PI
: M.H. Xie (HKU)
Co-PIs: X.D. Cui (HKU), S. Zhang (HKU), D.K. Ki (HKU), H. Zhang (CityU), J.B. Xu (CUHK), S. Yang (CUHK), S.P.D. Lau (PolyU), N. Wang (HKUST), K.T. Law (HKUST)
Co-Is: J.H. Hao (PolyU), J.N. Wang (HKUST), Z.Y. Meng (HKU), T.T. Luu (HKU), W.D. Li (HKU), D.Y. Lei (CityU)
Collaborators: X.D. Xu (Univ. of Washington, Seattle), C.H. Jin (Zhejiang Univ.), M. Chhowalla (Cambridge), K.P. Loh (National Univ. of Singapore), Y.G. Ma (Zhejiang University), K.F. Mak (Cornell University)

The rapid development of information technology has been based on the continuous scaling down of microelectronic devices that improves cost, performance and power. This trend, empirically summarized as Moore's law, is coming to an end because of the intrinsic scale limit of silicon microelectronics. The new era of innovation will be profoundly different, calling for: new material systems to host even smaller devices under new geometry, new heterogeneity, new quantum degrees of freedom to carry information, and new physical principles to process and store information.

Two-dimensional (2D) materials have a great potential to revolutionize microelectronics and information technology. The variety of 2D materials feature a wide range of material properties from metal, semiconductors, insulators to magnets and superconductors, as well as exotic physics associated with electrons’ quantum degrees of freedom (spin & valley) that could be exploited to encode and process information more efficiently. Their tiny thickness - just a few atoms at most - promises the ultimate miniaturization of devices, and unparalleled control of materials and device functions. Moreover, 2D materials feature an unprecedented flexibility in their assembly into heterostructures, through which new materials and device functionalities may emerge. This project aims to explore these exciting opportunities for revolutionizing electronics, optoelectronics and photonics, through a concerted effort addressing the fundamental issues from physics, materials synthesis to device engineering based on 2D materials.

Led by pioneers in the field of 2D materials, this AoE project is an inter-institutional (involving 5 universities) and interdisciplinary one covering physics, applied physics, chemistry, electrical engineering. The team will seek to sustain Hong Kong’s edge in the field through basic and applied research, with a long-term goal of developing new prototype devices that will have application and commercialization potentials for Hong Kong.

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Area of Excellence

on Probing the Fundamental Structure of Matter with High Energy Particle Collisions

Project Coordinator: M.C. Chu (CUHK)
: A. Cohen (HKUST), L.R. Flores Castillo (CUHK), Z.C. Gu (CUHK), W.H. Ki (HKUST), J.H.C. Lee (HKU), P.P.C. Lee (CUHK), T. Liu (HKUST), E. Lo (CUHK), K. Prokofiev (HKUST), K.P. Pun (CUHK), C.Y. Tsui (HKUST), Y.J. Tu (HKU), H. Tye (HKUST)
Co-Is: K.B. Luk (U.C. Berkeley and HKUST), C. Young (SLAC National Accelerator Laboratory and CUHK)
Collaborators: M. Kado (Laboratoire de l'Accélérateur Linéaire, Universite Paris-Sud), A. Lounis (Laboratoire de l'Accélérateur Linéaire, Universite Paris-Sud), S. McMahon (Science and Technology Facilities Council), A. Schaffer ((Laboratoire de l'Accélérateur Linéaire, Universite Paris-Sud), B. Zhou (University of Michigan)

The discovery of the Higgs boson (popularly known as ‘the God particle’) at the Large Hadron Collider (LHC) at CERN marked the beginning of a golden age for fundamental physics. The Higgs boson is an elementary particle that interacts with leptons, quarks, and weak force carriers to give them their masses, via a new fundamental force. One of the most important tasks in fundamental physics today is to measure and characterize the properties of the Higgs boson including its interactions with other elementary particles. The Higgs boson may also open up a new window to physics Beyond the Standard Model (BSM) if it couples to hidden particles, such as dark matter particles. There may be more than one Higgs particle, as predicted in many BSM theories. In the next decade, the LHC will undergo two more upgrades, so as to reach the unprecedentedly high center-of-mass energy of 14 TeV and intensity 5-7x1034 cm-2s-1, greatly extending its sensitivity for new physics. With the support of 3 previous CRF grants, the project team has established itself as an active member of the ATLAS experiment at the LHC and as one of the most active particle theory groups in the region. We are fortunate to be at the right time and in the right place to seize the emerging opportunities to make breakthrough discoveries that may revolutionize our understanding of the fundamental structure of matter. We have carried out fundamental work on the Higgs particle, establishing its spin and parity, couplings to Standard Model (SM) particles, and designed new strategies for probing BSM physics. We have developed analysis tools and built an ATLAS Tier-2 computing center in Hong Kong. We plan to build upon our existing strengths in particle physics to measure the Higgs properties, search for BSM physics, develop particle physics theories, contribute to the ATLAS detector upgrade and to the R&D for the proposed Circular Electron-Positron Collider (CEPC) in China, and develop improved techniques in Big Data computing and machine learning. The proposed project is at the forefront of particle physics research and will enable Hong Kong to take full advantage of emerging opportunities. Our project will substantially raise the profile of Hong Kong scientists and their global impact, attract students to STEM subjects, and promote interdisciplinary research in physics, electronics, detector development, computing and data science.


Area of Excellence

on Theory, Modeling, and Simulation of Emerging Electronics

Project Coordinator: F.C. Zhang (HKU)
J. Wang (HKU), G.H. Chen (HKU), L.J. Jiang (HKU), H. Guo (McGill and HKU), W.C. Chew (UIUC and HKU), M.S. Chan (HKUST), P.C.H. Chan (PolyU)
Co-Is: X.D. Cui (HKU), W. Yao (HKU), E. Lam (HKU), D.S.H. Lo, (HKU), P.W.T. Pong (HKU), N. Wong (HKU), K.L. Wu (CUHK), J.N. Wang ( HKUST), Y.J. Yan (HKUST)

This is a multi-institutional interdisciplinary project held by The University of Hong Kong, The Hong Kong University of Science and Technology, and The Chinese University of Hong Kong, and is funded by the Areas of Excellence Scheme. The current project team comprises Professor Fu-Chun Zhang (Physics, HKU), Professor Philip Chan (Provost, PolyU), Professor Guanhua Chen (Chemistry, HKU), Professor Weng-Cho Chew (EE, HKU), Professor Hong Guo (Physics, McGill Univ.), Professor Jian Wang (Physics, HKU), and several co-investigators.

The project strives to develop a suite of multi-scale electronic design automation (EDA) tools ranging from atomistic simulation methods to circuit simulators and to electromagnetic solvers for electrical signals for emerging sub-22nm technology. With these tools, we will study the sub-22nm devices and their systems; and calculate their physical and dynamical properties, and explore the possible paradigm shifts of next generation electronics. Our objectives are specifically listed below:

  • To simulate from first-principles the electrical properties and processes of sub-22nm devices with atomistic details
  • To investigate lithography modeling, and to employ efficient electromagnetic solvers to simulate electrical signals, power delivery, crosstalk, interference, and noise in multi-scale complex integrated circuits
  • To calculate and model the electrical, chemical and mechanical properties of new materials for sub-22nm technology
  • To develop modeling tools for emerging spintronics
  • To use electron beam lithography technology to fabricate the sub-22nm devices for measurement and calibration of the parameters in our EDA tools
  • To develop a set of multi-scale EDA tools for emerging devices and integrated circuits

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CRF (Collaborative Research Fund) Awards in HKU Physics




Transport and dynamics of correlated quantum matter
Project Coordinator: S.Q. Shen (HKU)
Co-PIs: G. Chen
 (HKU), Z.C. Gu (CUHK), X. Li (CityU), C.J. Wang (HKU), S.Z. Zhang (HKU)

Dynamics and transport properties of interacting many-body physics constitute one of the most important problems in modern condensed matter physics. Conventional theories on transport such as Boltzmann equations rely on being able to describe the system as a congregation of weakly interacting particles. However, when interaction becomes very strong, as in the case of materials that are close to their quantum critical points or unitary Fermi gas, the quasi-particles are presumably not well defined and a reliable theoretical framework for transport is missing. The topology of the band structure in solids also strongly modifies the usual transport equations and leads to novel transport effects. In some correlated quantum matter, topologically nontrivial low-energy excitations become the main carriers for charge, spin and heat transport, giving rise to new phenomena. Another class of systems that cannot be captured by the conventional Boltzmann equation approach are those far from thermal equilibrium. In particular, novel nonequilibrium phases of matter such as many-body localization, discrete time crystals, and quantum many-body scar states have emerged in recent years as promising platforms for quantum control and quantum simulation purposes. In particular, the memory of the initial state in such systems may be retained for an extended period, making them useful for quantum information storage applications. The dynamic and transport properties of quantum systems determine potential applications of quantum materials in the future.

The objectives of the project are (1) to investigate the transport and dynamics in which band topology plays a crucial role; (2) to investigate the transport and dynamics in strongly interacting and correlated systems; and (3) to develop and apply new numerical techniques for calculating transport and dynamic properties in the correlated quantum systems. The team are expected to contribute new understandings of various transport and dynamic phenomena, to explore new effects and novel states of matter in condensed matter and cold atom systems, to form a strong team at the forefront in the proposed field with an impact on the international community, and to train Ph. D students who could be contributing as researchers in academia or industry and become productive members of the society. In the long term, it is expected that the research work would possibly help the area of identifying and understanding correlated quantum materials to realize application in industry such as topological electronic devices and quantum computation qubits.



Low-dimensional perovskite materials for efficient and stable light emitting diodes: Materials, devices and fundamental understanding
Project Coordinator: W.C.H. Choy (HKU)
A.B. Djurišić (HKU), A. Rogach (CityU), H.B. Su (HKUST), K.S. Wong (HKUST), N. Zhao (CUHK)
Collaborators: O. Abdelsaboor (KAUST), Y.Z. Jin (ZJU)

Low-dimensional halide perovskite emitters including zero-dimensional quantum dots (QDs) and quasi two-dimensional (quasi-2D) perovskites with the advantages of quantum confinement effects have emerged as a novel class of revolutionary semiconductors with high color purity, wide color gamut, low cost and simple solution process for vivid natural-color yet cost-effective displays. However, perovskite materials commonly exhibit environmental instability due to humidity, light and/or elevated temperature significantly hindering their applications in light emitting diodes (LEDs) where reported lifetimes are commonly in the order of minutes. Furthermore, while blue, green, and red emitters are the primary components for display applications, the efficiency of blue emitters presently lags behind green/red emitters. Despite the daunting challenges, the properties of both classes of low-dimensional perovskite emitters are extremely sensitive to their compositions and synthesis conditions, which opens up potential pathways for enhancing both the photoluminescence quantum yield and environmental stability through designing the composition, structure and quality of the perovskites. Meanwhile, in order to achieve well performing and stable multilayer-structured perovskite LEDs (PeLEDs), present studies on materials of charge transport layers, interfacial engineering, and defect passivation are critical yet still inconclusive. Additionally, device physics, operation and degradation mechanisms are crucially important for both optimizing the device performances and understanding the deterioration of the performance over time to achieve the practical applications of PeLEDs. We propose to perform a comprehensively study of theoretical modeling and experimental analysis of PeLEDs covering materials, devices, and the underlying understanding of related physical processes. We aim to (1) fundamentally understand the relationship between low-dimensional perovskite synthesis and composition, nucleation, and the formation of non-radiative defects, (2) develop practical material synthesis approaches for highly luminescent and stable perovskite emitters, (3) establish device architectures yielding high performances in PeLEDs, (4) elucidate the relationship between the materials in multilayered structures and device performances, and (5) achieve state-of-art low-dimensional PeLEDs.



New phases of quantum matter in engineered atomic systems
Project Coordinator: G.B. Jo (HKUST)
D. Wang (CUHK), Z.D. Wang (HKU), S.Z. Zhang (HKU)

The ever-increasing demand for new quantum matter has driven the engineering of synthetic systems. Among many candidates, ultracold atoms and molecules provide synthetic quantum materials whose system properties can be freely tuned on demand. This maneuverability offers a great opportunity to discover new phases of quantum matter which can drive and revolutionize modern technologies.
Over the past few years, we have witnessed unprecedented advances in our understanding of quantum matter in the presence of non-trivial topology, dissipation, and interactions that are ubiquitous in nature. Nevertheless, our understanding of such cutting-edge quantum matter is often impeded by the inherent complexities in the system. Our CRF project aims to overcome this problem by using engineered atomic systems through which experimental studies can be coherently integrated with minimal theoretical models in a controlled manner.
In our proposed project, we will quantum-simulate fundamental Hamiltonians with non-trivial topology, interactions, and dissipations, and then develop a set of advanced tools and methods for emulating new phases of quantum matter comprising ultracold atoms, molecules, and photons. To create, characterize, and understand the physical principles behind new quantum matter, various state-of-the-art platforms will be used by three experimental groups (GB Jo, SW Du, and D Wang) in close collaboration with two theoretical groups (Z Wang and S Zhang) in the CRF team. The investigated systems include spin-orbit-coupled cold atoms, a highly nonlinear atomic medium, and ultracold polar molecules. We will explore the following directions that result in the unconventionality of the atomic Hamiltonian: (1) non-trivial band topology, (2) non-Hermiticity, and (3) synthetic dimension.
The proposed research goals are highly interdisciplinary and require a collaborative approach in our CRF team. Our team members have already collaboratively performed several research works in the preliminary stage. The CRF grant will further deepen the collaboration among quantum physicists in Hong Kong and will produce cutting-edge research results that can be recognized by the international community.




Dark Matter and the Universe
Project Coordinator: T. Liu (HKUST)
T. Broadhurst (HKU), A. Cohen (HKUST), J.J.L. Lim (HKU), G.F. Smoot (HKUST), H.S.H. Tye (HKUST), Y. Wang (HKUST)
Collaborators: T. Chiueh (NTU), M.C. Chu (CUHK), J. Ren (IHEP), R.A. Windhorst (ASU), Y. Zhao (The University of Utah)

Dark matter (DM) is one of the most mysterious cosmic puzzles, uncovered by wide-ranging observations from cosmic microwave background to large-scale structure and galaxy rotation. Astrophysicists and cosmologists have accurately established that DM comprises 84% of the matter in the universe, with only 16% in stars and gas. Decades of study has converged on a consensus that DM must be predominantly some form of unknown massive particles, the nature of which is being vigorously explored at the frontier of astrophysics, cosmology and particle physics in a combined interdisciplinary effort, although part of it could be still explained by astrophysical objects such as primordial black holes (PBHs). This consensus naturally raises the question how to accommodate such DM particles into the theory of particle physics, as no suitable DM candidate exists in its Standard Model.
Ingenious hypothetical extensions to particle theory have been proposed in the past decades. Among them the paradigm of weakly interacting massive particles (WIMPs), resting on the so called “WIMP miracle”, is especially influential. This idea potentially unites DM with physics which dynamically drives electroweak symmetry breaking. It accounts for the relic abundance of DM, predicts the individual DM particle mass to be of electroweak scale, and can be responsible for the Higgs particle discovered at Large Hadron Collider (LHC). However, no such particles have materialized at LHC or elsewhere. This situation drives scientists to reevaluate exiting DM theories and detection strategies, and develop new ideas.
In this CRF project, we propose to utilize the expected data of James Webb Space Telescope (JWST) to explore the nature of DM, by synergizing the expertise of particle physicists, astrophysicists and cosmologists in Hong Kong. The space telescopes such as Hubble and Spitzer generated far-reaching impacts for the DM study in history. As their successor, JWST owns unprecedented capability of imaging the lensing objects or clusters in both near and mid infrareds. This will allow us on the one hand to constrain the proportion of DM in the form of PBHs, and on the other hand to determine the favored DM candidate between the WIMP and fuzzy DM (one representative alternative to the WIMP). With these efforts, we expect that the Hong Kong team will, for the first time in the world, provide a world-leading picture on the nature of DM based on the JWST data.


HKU, PolyU

Controlling the moisture – towards stable and efficient flexible perovskite solar cells
Project Coordinator: A.B. Djurišić (HKU)
S.P.T. Feng (HKU), G. Li (PolyU), W. Li (HKU), J.Y. Tang (HKU)

Perovskite solar cells (PSCs) exhibit the highest efficiency among emerging low-cost photovoltaic technologies (>25%), but they also exhibit sensitivity to moisture, illumination, and elevated temperature, which needs to be resolved for their commercialization. To fully realize the cost advantage of this technology, flexible substrates compatible with roll-to-roll printing need to be used. However, stability problems are even more critical for flexible PSCs. In addition to the worsening of ambient stability due to higher oxygen and moisture permeability of flexible plastic substrates, mechanical stress causes degradation of performance due to increase in the sheet resistance of commonly used indium tin oxide coated plastic substrates.
To address these issues, we propose to develop stable and efficient flexible PSCs on customized polymer substrates. To solve the problem of degradation under mechanical stress, we will use multilayer electrode consisting of a flexible metal grid embedded into the polymer substrate, coated with conductive material for corrosion protection and improved charge collection. To solve the problem of moisture permeability through the substrate and PSC sensitivity to moisture, we will deposit barrier layers to enhance hydrophobicity of the polymer substrate and reduce water vapor transmission ratio, and we will use 3D/2D active perovskite layers with improved ambient stability. To further improve the stability and address the issue of ion migration in the devices, we will incorporate interfacial layers using organic molecules which display ability to adsorb iodine (for example, phthalocyanines, porphyrins and related analogues) and thus provide significant suppression of ion migration. Finally, we will develop encapsulation techniques and materials for the encapsulation of flexible PSCs which will enable long-term stability, as well as prevent leaching out of Pb from the active layer to achieve safeby-design PSCs. Utilizing these innovative strategies, we aim to achieve flexible PSCs with high efficiency (19%) and excellent stability, namely stabilized T80 exceeding 1000 h under different ISOS protocols, including outdoor testing. Thus, the long-term stability of the devices will be evaluated by comprehensive testing according to different ISOS protocols taking into account recent protocol updates for PSC testing. We will quantify the contributions of the substrate, encapsulation and the intrinsic device instability to the overall performance degradation, and we will also determine acceleration factors for different accelerated aging protocols to establish links between lifetimes during accelerated aging protocols and realistic outdoor lifetime.



Measurement of the Neutrino Mass through the Effects of Relic Neutrinos on Cosmological Structure
Project Coordinator: J.J.L. Lim (HKU)
T. Broadhurst (IKERBASQUE), J. Cenarro (CEFCA), M.C. Chu (CUHK), G. Smoot (UST) 
Collaborators:  L.R. Abramo (University of Sao Paulo), R.E. Angulo (DIPC), N.A. Bahcall (Princeton University), S. Bonoli (CEFCA), J.J.G. Cadenas (DIPC), Y.F. Cai (University of Science and Technology of China), K.C. Chan (Sun Yat-Sen University), J.M. Diego (IFCA), T. Dinh (Vietnam Academy of Sciences), R.A. Dupke (National Observatory of Brazil), R. Emami (Harvard-Smithsonian Center for Astrophysics), N. Kaiser (ENS), X. Kong (University of Science and Technology of China, W.T. Luo (Kavli IPMU), C.Y. Ng (HKU), M. Oguri (University of Tokyo), K. Umetsu (ASIAA), J.M. Vilchez (IAA), A. Zitrin (University of the Negev)

By combining expertise in astronomical measurements at HKU, cosmological simulations at CUHK, and theoretical cosmology at HKUST, we have made a preliminary determination of the absolute neutrino mass scale:P m =(0:110:03)eV. This value is consistent with the minimum mass of 0.1 eV permitted by the inverted neutrino mass hierarchy, but not sufficiently precise to discriminate between this and the even lower minimum mass of 0.06 eV permitted by the normal hierarchy. Here, we seek to confirm our preliminary measurement by gathering more comprehensive astronomical data and conducting more exacting cosmological simulations, thus improving upon our measurement precision such as to potentially discriminate between the two neutrino mass hierarchies. A precise mass measurement will aid complementary laboratory experiments to determine the ordering of the neutrino mass hierarchy, and together guide physics beyond the Standard Model.
The Standard Model of particle physics unifies the strong, weak, and electromagnetic forces, as well as classifying all known elementary particles. This pillar of modern physics is, nonetheless, incomplete. In its current formulation, the three known types of neutrinos – the electron, muon, and tau “flavours” – should have no mass. The surprising discovery that neutrinos can change from one flavour to another, however, requires neutrinos to have mass. It is now understood that a neutrino of a specific flavour is each associated with a specific quantum superposition of three mass eigenstates having masses of m1, m2, and m3. The sum of the three mass eigenstates is simply referred to as the “neutrino mass,”P m =m1 +m2 +m3. The nonzero mass of neutrinos drives intensive major worldwide efforts to determine the neutrino mass, along with the ordering of its mass hierarchy: that is, whether m1
By measuring the probability of flavour changes as a function of neutrino energy and distance propagated, laboratory experiments are defining the values of neutrino oscillation parameters with increasing precision, thereby setting firm lower limits on the neutrino mass for either the NH and IH. One of these parameters, the mixing angle 13, was first determined by the Daya Bay Reactor Neutrino Experiment, in which Hong Kong-based scientists played a leading role. The value of this parameter turned out to be surprisingly high, motivating future experiments to examine whether neutrinos violate charge-parity symmetry, which may then explain why there is far more matter than antimatter in the Universe. These experiments also promise a determination of the neutrino mass hierarchy, with current data favouring the NH. Some laboratory experiments even hint at the existence of additional neutrino species.
At present, cosmological data, rather than laboratory experiments, provide the most stringent constraints on both the number of neutrino species and the neutrino mass. Because neutrinos were created in abundance during the Big Bang, their properties can be measured through their effects on Big Bang nucleosynthesis and the Cosmic Microwave Background (CMB). CMB measurements imply a total of three relic neutrinos species – as in the Standard Model – that slightly smoothed matter density fluctuations in the early Universe, and which are predicted to continue suppressing the growth of cosmological structure throughout subsequent cosmic history. We have measured this suppression for the first time by comparing thousands of galaxy clusters with theoretical computations and computer simulations of cosmologial structure formation defined using precise CMB measurements, thus leading to a first preliminary inference of the neutrino mass. To maintain momentum and cement Hong Kong at the forefront of this breakthrough, we propose to robustly confirm and measure with greater precision the neutrino mass by participating in a telescope survey ideally suited for studying galaxy clusters, and continuing the development of state-of-the-art cosmological simulations for exacting predictions regarding the effects of relic neutrinos on the growth of cosmological structure.



Quantum State Manipulation of Ultracold Atoms in Optical Lattices
Project Coordinator: S. W. Du (HKUST)
G.B. Jo (HKUST), D.J. Wang (CU), Z.D. Wang (HKU), S.Z. Zhang (HKU)

Atoms are the building blocks of our material world. Manipulating the quantum states of atoms in a controllable way is important not only for understanding of fundamental quantum physics, but also for laying the foundation for next-generation functional materials and quantum technologies. In this regard, a dilute gas of ultracold atoms is an ideal platform because of its unprecedented flexibility stemming from its versatile and high precision interactions with electromagnetic waves.
In this proposed project, based on our already established strengths in experimental and theoretical research in ultracold atoms, we will explore exotic many-body quantum physics with ultracold atoms in optical lattices and subject to synthetic gauge potentials. Our proposed studies will be carried out in two distinct systems different from those in most previous investigations: a) we make optical lattices with alkali-earth-like ytterbium atoms, which features very narrow optical transitions allowing very high precision detection and manipulation of the atomic states; b) we apply species-selective optical lattices to a Bose-Bose mixture with spin degrees of freedom and explore physics arising from the interspecies spin-exchange interactions.
The proposed research activities involve several different areas of atomic and optical physics and are highly collaborative in nature. The three experimental groups will join forces to realize optical lattices with various high tunable geometries in both systems and to explore the generation of synthetic gauge potentials using various strategies. Myriads of theoretical ideas already put forward by the three theoretical members and other groups, including many-body physics of interacting bosons and fermions in unconventional bands (such as the flat and topological ones), and dynamics of Bose-Bose spinor mixture with gauge potentials (such as spin-orbit coupling), can then be investigated.
Our experimental settings are analogous to electrons in crystal lattices subject to real electromagnetic waves, but the high flexibility of ultracold atoms allows us to sample physics both within and beyond solid state materials. The findings in our research will undoubtedly deepen our understandings of many-body quantum physics and aid the design of new quantum materials.
Another important goal of this proposed project is to further strengthen the cold atom research community in Hong Kong which is already recognized worldwide as a new rising power. The CRF grant will formally bind all the local cold atom groups together and provide us with a collaboration platform to carry out frontier research in quantum physics.




Two-dimensional Transition-metal Dichalcogenides and Beyond - From Materials, Physics to Devices
Project Coordinator: M. H. Xie (HKU)
X.D. Cui (HKU), S.Q. Shen (HKU), W. Yao (HKU), J.N. Wang (HKUST), N. Wang (HKUST), J.H. Hao (PolyU)

Two-dimensional (2D) materials are at the center stage of condensed matter and material science research today. Besides transition-metal dichalcogenides (TMDs), which are the subject of our on-going collaborative research project, an increasing number of new 2D systems have been identified and suggested to be of high application potentials. Examples of the latter include single-layer black phosphorus, (Ga,In)Se, MnPX3(X=S, Se), CrSiTe3, and chromium halides (CrBr3, CrI3, RuCI3) that show magnetic orders in the 2D forms.

In the course of the on-going TMD research, the team members have made internationally recognized achievements and produced impactful results. Examples include experimental observations of spin and valley polarizations, record high electrical carrier mobility and quantum transport anomalies. On theory, we revealed magneto-optical properties of excitons and trions in monolayer WSe2, found topological mosaic in moiré superlattices of van der Waals heterobilayers. The team members have also embarked on researches of other 2D systems such as black phosphorus and (Ga,In)Se by experiments, CrSiTe3 and halides by theory. In this renewal application, we will build upon our strength and past achievements in TMD research and to extend our studies of some other 2D materials like single-layer phosphorus, (Ga,In)Se, and magnetic 2D films. Specifically, we will make concerted efforts by combining theory and experiments to fabricate high quality 2D samples, their hybrid and heterostructures for characterizations of novel electronic, magnetic and optical properties as well as new physics. We shall explore application potentials of these 2D materials and structures by fabricating conventional or new-concept devices and to test their performances and functionalities. The team will continue to make impactful research outputs and contribute to the advance of 2D research in both fundamental physics and applications.



Study of Topological Phases in Condensed Matter and Cold Atom Systems
Project Coordinator: K. T. Law (HKUST)
T.K. Ng (HKUST), S.Q. Shen (HKU), S.Z. Zhang (HKU), Q. Zhou (CU)

Ordinary band insulators cannot conduct electricity due to the presence of a band gap and it takes energy larger than the band gap to excite electrons in the material. Recently, new types of band insulators, called topological insulators, have been discovered. Topological insulators have a band gap in the bulk, similar to ordinary band insulators, such that exciting electrons in the bulk costs finite energy. However, topological insulators support conducting surface states and electric currents can be driven by an arbitrary small electric field.

Recently, it was realized that some superconductors, called topological superconductors, possess bulk single-particle excitation band gap and support gapless excitation modes on their surfaces. The zero energy surface modes of these topological superconductors are called Majorana fermions. A Majorana fermion is an exotic particle, which may have applications in quantum computation. The study of both topological insulators and superconductors is now one of the central topics in condensed matter physics.
In the past few years, more topological phases, such as quantum anomalous Hall insulators and topological crystalline insulators, and nodal topological phases such as Weyl semimetals have been discovered theoretically and experimentally in condensed matter systems.
Remarkably, as studies of topological matter flourish, independent developments in the study of cold atoms, creating synthetic gauge fields and spin-orbit coupling between atoms, have brought these two exciting developments together. The reason is that spin-orbit coupling is the basis for the construction of many types of topological matter, and the great flexibility of cold atom experiments raises the possibility of creating many topological states that are hard to achieve in condensed matter systems, as well as realizing new fundamentally interesting topological states unique to cold atoms.
Our project combines the existing strength of researchers in the areas of topological order of condensed matter systems (KT Law, TK Ng and SQ Shen) and of cold atoms (SZ Zhang and Q Zhou), building a strong theoretical research team based in Hong Kong to explore this new and exciting area of research. The team is expected to produce results at the forefront of this new area of research, with a long-term impacts on the international community. We will also cultivate a new generation of theoretical physicists in Hong Kong who can explore frontier topics in both condensed matter physics and in cold atomic systems.



Two-Dimensional Transistion-Metal Dichalocigenides - from Materials, Physics to Devices
Project Coordinator: M. H. Xie (HKU)
X.D. Cui (HKU), S.Q. Shen (HKU), W. Yao (HKU), J.N. Wang (HKUST), N. Wang (HKUST), J.H. Hao (PolyU)

Atomically thin two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are attracting high interests due to their novel properties as well as the ultimate miniaturization in thickness that promises nano-electronics and nano-optoelectronics. They are semiconductors with multi-valley band structures where electrons are labeled both by the spin and valley pseudo-spins, offering ideal platforms to exploring new concept devices utilizing these internal degrees of freedom. Their visible frequency range direct band-gap is ideal for optoelectronic and solar energy applications.

Bulk TMDCs exist in the form of stacks of covalently bonded hexagonal quasi-2D lattices packed by weak van der Waals forces. Flakes of monolayer TMDCs can be prepared by micromechanical cleavage (e.g., using Scotch tape) and by ion- intercalation, for example. Using the “flake” samples, people have discovered interesting properties of these 2D materials. Prototype devices have been made to demonstrate the concepts and viability of using gapped 2D semiconductors for electronic devices. However because the flake samples are small and not very reproducible, explorations of such materials remain hindered by the availability of high quality wafer-scale samples. There is an increasing demand of better and wafer sized samples for characterization and device fabrications.

In this proposal, we bring together a team of active researchers of complementary background and expertise for a concerted effort aiming at (1) producing high quality wafer scale 2D TMDC samples; (2) exploring spin and valley related new physics and properties of 2D TMDCs and examining the effects of defects; (3) experimenting device fabrication and characterization. The collaboration of theoretical and experimental teams in this proposal will ensure a comprehensive and productive research program, leading to new findings that likely impact on the advance towards future nano- electronics and nano-optoelectronics.



New Topological States in Cold Atom and Condensed Matter Physics Systems
Project Coordinator: T.K. Ng (HKUST)
K.T. Law (HKUST), S.Q. Shen (HKU), S.Z. Zhang (HKU), Q. Zhou (CUHK)

Topological state of matter is now considered to be the most exciting area of research in hard condensed matter physics because of their rich new physics, and because of their exciting promise for application in quantum information. Remarkably, as activities in topological matter flourishes, an independent dramatic development in cold atoms on the creation of synthetic gauge fields and spin-orbit coupling between atoms have brought these two exciting development together. The reason is that spin-orbit coupling is the basic ingredient for the construction of many topological matters, and the great flexibilities of cold atom experiments raises the hope to realise many topological states hard to achieve in condensed matter systems, as well as to realise many new topological states of fundamental interests unique to cold atoms. Our project combines the existing strength of researchers in the area of topological order at condensed matter systems (TK Ng, KT Law and SQ Shen) and researchers in Cold atoms (S.Z. Zhang and Q. Zhou) to build a strong theoretical research team to explore this new and exciting area of research.



Searching for New Physics with the Large Hadron Collider
Project Coordinator: M.C. Chu (CUHK)
H.F. Chau (HKU), L. Flores Castillo (U. of Wisconsin), K.B. Luk (U.C. Berkeley and HKU), G.M.L. Shiu (HKUST), C. Young (Stanford Linear Accelerator Center and CUHK)

Built upon our successful experience in the Daya Bay Reactor Experiment and the supporting Aberdeen Tunnel Experiment, and the strong collaboration both between institutions in Hong Kong and between the Hong Kong team and leading institutes overseas and in China, we propose to form a Hong Kong experimental particle physics group to join the ATLAS Collaboration, one of the two major Large Hadron Collider (LHC) experiments at CERN. Deploying the largest detectors and highest energy particle accelerator in the world, the LHC experiments are well positioned for making breakthrough discoveries in fundamental physics. The LHC runs in 2011-3, even though still at roughly half of the designed energy, already produced a huge volume of data. The discovery of the Higgs particle is indeed a result of these runs. We plan to take up tasks on physics analysis of the data accumulated so far, to search for new physics beyond the Standard Model of Particle Physics, and on software development so that the analysis tools will be ready when the beam energy and luminosity both increase drastically with the new LHC run, in 2014.We plan to carry out analysis of the Higgs particle and search for heavy weak bosons W’ and Z’, supersymmetric partners, and dark matter particles. The upcoming upgrade of the ATLAS detector presents a window of opportunity for Hong Kong researchers to contribute to the hardware development of the ATLAS experiment. In particular, we will work on the hardware development, reconstruction and simulation of the muon system. This Hong Kong experimental particle physics group will be an important component of the newly formed Joint Center for Fundamental Physics, by physicists in CUHK, HKU, and HKUST. The group will also benefit from interacting with the particle theory and astrophysics groups under the Joint Center of Fundamental Physics. With the manpower and resources from CUHK, HKU and HKUST together, we believe we can make meaningful contributions to experimental particle physics, one of the most important endeavors in human being’s quest to understanding Nature.



Research in Fundamental physics: from the Large Hadron Collider to the Universe
Project Coordinator: G.M.L. Shiu (HKUST)
H.S.H. Tye (HKUST), T. Liu (HKUST), H.B. Li (CUHK), K.S. Cheng (HKU)

Fundamental physics addresses some key questions of Nature: What are we made of? What are the fundamental forces and matter in Nature? What is the origin of our Universe? These questions are intimately connected. Although key questions in fundamental physics are few, in contrast to other areas of scientific research, they are some of the most challenging ones in science. Advance towards their comprehension and solution requires big teams of experimentalists to extract important data, whose implications lead theorists to explore new possibilities and to make the predictions for experimentalists to test.

With the discovery of the Higgs particle at CERN’s Large Hadron Collider (LHC) in the past year, we now have a rather complete picture of what we are made of: electrons, quarks and gluons, the latter two combine to form protons, neutrons and nuclei, while the masses of fundamental particles (electrons, quarks etc.) come from the Higgs field.

Meanwhile, game-changing discoveries in astrophysics and cosmology have shaped our understanding of Nature at large scales. Observational data reveal that all known matter constitutes less than 5% of the total energy-matter content of the universe, and the remaining 95% is made up of dark matter and dark energy. While the observational evidence for dark energy (Nobel Prize 2011) is compelling, its theoretical underpinning remains a great mystery. Likewise, the existence of dark matter opens the next frontier in particle physics: the search for new physics beyond the Standard Model that we now know. Importantly, physics of the large and the small are deeply intertwined. With precise data, we can probe with high accuracy the early universe where fundamental physics leaves its fingerprints. These measurements provide strong support for cosmic inflation in which the early universe was driven by an enormous dark energy, thus explaining the origin of the hot big bang.

Fundamental physics is a brand new initiative in Hong Kong. This proposal focuses on its theoretical aspects because we have now a critical mass of theoretical physicists in Hong Kong working on these areas while the experimental program is actively being developed. As fundamental physics enters a data-rich era, it is crucial for theorists and experimentalists to collaborate closely. Theoretical studies are key to understanding the vast amount of data and designing new search strategies. Our team comprises researchers with complimentary expertise in a wide range of interconnected areas in particle physics, astrophysics, and cosmology.



Quantum Control and Quantum Information Processing
Project Coordinator: Z.D. Wang (HKU)
W. Yao (HKU), H.F. Chau (HKU), R.B. Liu (CUHK), S. Du (HKUST)

Quantum control and quantum information processing using atomic optical systems and solid state systems are cutting edge sciences with applications in device science, communication, cryptography, and metrology. In this collaborative project, we bring together the existing research strength in these areas in Hong Kong to form a team to address important issues in these areas. In particular, we will concentrate on the experimental studies on quantum state control, quantum information processing, and quantum communications using systems including photons, atoms and artificial atoms in solids. These studies will be backed up by the theorists in our team. We expect that the collaborative research in this emerging interdisciplinary field will not only advance our understanding of the exotic quantum world, but also expand our imagination for tomorrow’s quantum technological innovation.



Nano-Spintronics - Quantum Control of Electron Spins in Semiconductors
Project Coordinator: F.C. Zhang (HKU)
Co-Is (HKU-Physics):
X.D. Cui, S.Q. Shen, M.H. Xie

Spin based electronics or spintronics as a new generation of electronics is an emerging field with a great promise to advance the semiconductor industry. Spintronics aims to use electron’s spin, a tiny magnet or compass, to replace the role of electric charge in electronics. Metallic spintronics has already had a lot of applications. One of the recent focuses is the generation, manipulation and detection of spin-current, a counterpart of charge current, which may open a new route in the future spintronics. In this group project we will consolidate the existing research strength in both experiment and theory to form a versatile team in Hong Kong to focus on the generation and detection of the spin current.



Quantum Order in Novel Materials: Superconductivity and Topological Order
Project Coordinator:
Co-Is (HKU-Physics):
 S.Q. Shen, Z.D. Wang, and F.C. Zhang

Iron-based (pnictides) superconductors and topological insulators are the most important discoveries in hard condensed matter physics in recent years. The two classes of materials exhibit the common feature of exotic quantum behaviors (quantum order). Elucidating the principles that govern the properties of these materials and exploring their technological implication are the goals of the physics community. The complexity in tackling the many intervening issues in this area calls for a collaborative approach. With the help of a previous Collaborative Research Grant, a research team to tackle this problem is ready. The proposal consolidates the team to study holistically the novel quantum order behind these materials and to explore the nature of general topological order, a key ingredient in quantum information science. Several team members have entered this new field with influential results already produced. The goal of the team is to continue the high-quality research and become internationally recognized.


CUHK, HKU, U.C. Berkeley (USA) and IHEP, CAS (China)

High Precision Measurement of Neutrino Oscillation at Daya Bay
Project Coordinator:
 M.C. Chu (CUHK)
Co-Is (HKU-Physics): 
K.S. Cheng, J.K.C. Leung and J.C.S. Pun

The recent discovery of neutrino oscillation – a neutrino travelling in space transforms from one type to another – has profound impacts on particle physics, astrophysics and cosmology. The Daya Bay Reactor Neutrino Oscillation Experiment aims to measure a key but yet unknown neutrino oscillation parameter, θ13, to an unprecedented precision of better than 3 degrees, which is critical to the design of future experimental tests of a possible explanation of why matter dominates anti -matter in the universe, a key condition for our existence.

The Hong Kong team has been an active member of the Daya Bay Collaboration, an international team with 38 institutions. We will contribute to the commissioning and monitoring of the experiment and analysis of data, with the help of a subsystem of the antineutrino detector built by our team. We will also design and construct a continuous radon monitoring system as well as a cover gas system to minimize radon contamination of the detectors.

More details please refer to here.



Studies of Fundamental Properties of Nanosurfaces and Selected Applications
Project Coordinator:
 M.A. Van Hove (CityU)
Co-Is (HKU-Physics):
A. Djurisic and H.S. Wu

The performance of nanoscale devices is often dominated by their surface properties. For example, surfaces introduce undesired electronic states in electronic and optoelectronic devices constructed from semiconducting nanostructures. By contrast, surface activity should be enhanced in nanostructures used as antibacterial agents. To improve such performance, our aim is to provide quantitative atomic-scale information about nanoscale surfaces. Our project will achieve this by introducing a new methodology: we will intentionally design and fabricate novel and highly-controlled nanoplatforms that allow for the first time detailed determination of surface structure and modeling of their relevant surface properties.

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RIF (Research Impact Fund) Awards in HKU Physics



HKU, Stockholm University, Gdansk University of Technology, Universitè Libre de Bruxelles

Trustworthy quantum gadgets for secure online communication
Project Coordinator: G. Chiribella (HKU)
Co-PIs: H.K. Lo
 (HKU), R. Ramanathan (HKU), K.Y.K. Wong (HKU), M. Bourennane (Stockholm University), P. Horodecki (Gdansk University of Technology), S. Pironio (Universitè Libre de Bruxelles)
Collaborators: J. Barrett (Oxford Uni.), F. Brandao (Caltech and Amazon)

Quantum cryptography promises a revolution in our communication technologies, offering enhanced security based on the fundamental laws of Nature. This level of security is essential to protect today’s sensitive information, such as census data, medical data, and industrial plans, from being decrypted in the future when more powerful computational resources will become available. In the short term, quantum cryptography can already benefit a vast range of applications, such as e-commerce, secure internet browsing, online messaging, online games, and online polls. Quantum cryptosystems have already been successfully employed to secure bank transactions, ballots, and, more recently, phone calls and video-conferences. If broadly implemented, they could benefit society at large, bringing unprecedented security and opening up a new market of quantum-enhanced products.

Still, the full potential of quantum security has not been realized yet. Commercial implementations are secure, but only as long as the devices behave according to their specifications. A new generation of quantum protocols, called device-independent (DI) and semi-device-independent (SDI) guarantee security even in the extreme scenario where the devices have been manufactured by the hackers themselves. However, DI/SDI protocols are still far from being practical. The goal of this project is to circumvent the roadblocks to DI/SDI cryptography, and to bring it closer to businesses and ordinary users. To achieve this goal, we have formed a world-class team including leading experts from the International Centre for the Theory of Quantum Technologies (Gdansk), Stockholm University, and Université Libre de Bruxelles. Building on a unique combination of expertise covering both theory and experiment, we will develop secure protocols for key distribution and random number generation that can be implemented on devices of moderate size while tolerating noise, imperfect initial seeds, and defects in the measurement devices.

This project will build up a local expertise in Hong Kong in the field of quantum cryptography, and is likely to spawn new start-up ventures in the near future. In the longer term, the development of quantum-enhanced communication systems will contribute to create a secure digital future and to strengthen Hong Kong’s leadership in the technological and financial sectors.

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