Condensed Matter Theory Group

Quantum computing by optical control in semiconductor

People

Research Activities

Theoretical condensed matter physics is a very important area in physical sciences because not only it concerns with many fundamental subjects but also it has very wide and potentially important applications in material science, biophysical science, high technology, and even economy and finance, etc. We have a very active research group in this field. Our current research interest includes:

1. strongly correlated electron systems;
2. theories for high temperature superconducting cuprates and iron pnictides;
3. quantum computation;
4. quantum magnetism;
5. spintronics and quantum transport.

Optical properties, including nonlinear optical properties, electronic structures, electron-phonon interactions, and ultrafast phenomena, in semiconductor nanostructures (e.g., quantum wells, dots and nanocrystals). The laboratory is equipped with variable-temperature (4.2K-300K) photoluminescence system, confocal micro-Raman system combined with a 77K-500K variable-temperature cooler, variable-temperature (10K-330K) broadband (200nm-1700nm) emission/absorption spectroscopy, ultrafast (sub-ps) time-resolved photoluminescence, and the near-field scanning optical microscopy.

(1) Prof. J. Wang: During the past ten years, our research evolves around the development of first principle quantum transport formalism as well as its practical implementation in nanoelectronics. On formalism developments, we have formulated a current conserving and gauge invariant theoretical framework based on the Keldysh non-equilibrium Green's functions to predict finite frequency AC as well as nonlinear DC quantum transport properties. In addition, we have combined the quantum transport theory and the density function theory and developed a start of the art first principle quantum transport theory (NEGF+DFT), calculation method, and computer code. Our method is the de facto standard technique for modeling quantum transport including all atomic, material and chemical details of the device.

(2) Prof. S.Q. Shen, an expert in the field of condensed matter physics, is distinguished for his research works on spintronics of semiconductors, quantum magnetism and orbital physics in transition metal oxides, and novel quantum states of condensed matters. He proposed theory of topological Anderson insulator, spin transverse force, resonant spin Hall effect and theory of phase separation in colossal magnetoresistive (CMR) materials. He proved existence of antiferromagnetic long-range order and off-diagonal long-range order in itinerant electron systems.

(3) Dr. W. Yao: We are a theoretical group working in an interdisciplinary field across condensed matter physics, quantum physics, and optical physics. Our research interests cover open quantum systems and quantum environment, quantum controls, cavity quantum electrodynamics, semiconductor optics, and topological quantum transport.  
 

Some Representative Publications

Prof. S.Q. Shen

1. "Massive Dirac fermions and spin physics in an ultrathin film of topological insulator", Hai-Zhou Lu, Wen-Yu Shan, Wang Yao, Qian Niu, and Shun-Qing Shen, Physical Review B 81, 115407 (2010)
2. "Topological Anderson Insulator", Jian Li, Rui-Lin Chu, Jainendra K. Jain, and Shun-Qing Shen, Physical Review Letters 102, 136806 (2009)
3. "Finite size effects of helical edge states in a quantum spin Hall system", Bin Zhou, Hai-Zhou Lu, Rui-Lin Chu, Shun-Qing Shen, and Qian Niu, Physical Review Letters 101, 246807 (2008)
4. "Spin transverse force on spin current in electric field", Shun-Qing Shen, Physical Review Letters 95, 187203 (2005)
5. "Resonant spin Hall conducatance in two-dimensional electron systems wit Rashba interaction in a perpendicular magnetic field", Shun-Qing Shen, Michael Ma, X. C. Xie, and Fu-Chun Zhang, Physical Review Letters 92, 256603 (2004)
6. "Spin Hall effect and Berry phase in two dimensional electron gas", Shun-Qing Shen, Physical Review B 70, 081311 (R) (2004)
7. "High Spin Systems with Orbital Degeneracy", Shun-Qing Shen, Xin-Cheng Xie and Fu-Chun Zhang, Physical Review Letters 88, 027201 (2002)]
8. "Antiferromagnetism and Phase Separation in Electronic Models for Doped Transition-Metal Oxides", Shun-Qing Shen and Z. D. Wang, Physical Review B 58, R8877 (1998)
9. "Ferrimagnetic long-range order in the Hubbard model", Shun-Qing Shen, Zhao-Ming Qiu and Guang-Shan Tian, Physical Review Letters 72, 1280-1282 (1994)
10. "Exact demonstration of off-diagonal long-range order in the ground state of a Hubbard model", Shun-Qing Shen and Zhao-Ming Qiu, Physical Review Letters 71, 4238-4240 (1993) 

Prof. J. Wang

1. "Controllable Andreev Retroreflection and specular Andreev reflection in a four-terminal Graphene-Superconductor hybrid system", S.G. Cheng, Y.X. Xing, J. Wang, and Q.F. Sun, Phys. Rev. Lett.  103, 167003 (2009).
2. "Universal quantized spin-Hall conductance fluctuation in graphene", Z.H. Qiao, J. Wang, Y.D. Wei, and H. Guo, Phys. Rev. Lett.  101, 016804 (2008).
3. "Persistent spin current in a mesoscopic hybrid ring with spin-orbit coupling", Q.F. Sun, X.C. Xie, and J. Wang, Phys. Rev. Lett.  98, 196801 (2007).
4. "Low-field phase diagram of the spin Hall effect in the mesoscopic regime", Z.H. Qiao, W. Ren, J. Wang, and H. Guo, Phys. Rev. Lett. 98, 196402 (2007).
5. "Universal spin-Hall conductance fluctuations in two dimensions", W. Ren, Z.H. Qiao, J. Wang, Q.F. Sun, and H. Guo, Phys. Rev. Lett.  97, 066603 (2006).
6. "ab initio modeling of quantum transport properties of molecular electronic devices", J. Taylor, H. Guo, and J. Wang, Phys. Rev. B 63, 245407 (2001).

Prof. Z.D. Wang

1. "Geometric Phase in Eigenspace Evolution of Invariant and Adiabatic Action Operators", C.Y. Teo and Z.D. Wang, Phys. Rev. Lett., 95, 050406 (2005).
2. "Geometric Quantum Computation and Multiqubit Entanglement with Superconducting Qubits inside a Cavity", S.L. Zhu, Z.D. Wang and P. Zanardi, Phys. Rev. Lett., 94, 100502 (2005).
3. "Vortex State in NaxCoO2• yH2O:px± ip - Wave Versus dx2-y2 ± idxy- Wave Pairing", Q. Han, Z.D. Wang, Q.H. Wang and T.L. Xia, Phys. Rev. Lett., 92, 027004 (2004).
4. "Unconventional Geometric Quantum Computation", S.L. Zhu and Z.D. Wang, Phys. Rev. Lett., 91, 187902 (2003).
5. "Vortex Charges in High-temperature Superconductors", Y. Chen, Z.D. Wang, J.X. Zhu and C.S. Ting, Phys. Rev. Lett., 89, 217001 (2002).
6. "Implementation of Universal Quantum Gates Based on Nonadiabatic Geometric Phases", S.L. Zhu and Z.D. Wang, Phys. Rev. Lett., 89, 097902 (2002).
7. "Nonadiabatic Noncyclic Geometric Phase and Ensemble Average Spectrum of Conductance in Disordered Mesoscopic Rings with Spin-Orbit Coupling", S.L. Zhu and Z.D. Wang, Phys. Rev. Lett., 85, 1076 (2000).
8. "Unified Theory of Mixed State Hall Effect in Type-II Superconductors: Scaling Behaviour and Sign Reversal", Z.D. Wang, J.M. Dong and C.S. Ting, Phys. Rev. Lett., 72, 3875 (1994).

Dr. W. Yao

1. "Quantum Computing by Optical Control of Electron Spins", R.B. Liu, W. Yao and L.J. Sham, Advances in Physics, 59, 703-802 (2010).
2. "Quantum Size Effects on the Work Function of Metallic Thin Film Nanostructures", J. Kim, S. Qin, W. Yao, Q. Niu, M.Y. Chou and C.K. Shih, Proceedings of the National Academy of Sciences of the United States of America, 107, 12761-12765 (2010).
3. "Optically controlled locking of the nuclear field via coherent dark-state spectroscopy", Xiaodong Xu, Wang Yao, Bo Sun, D. G. Steel, A. S. Bracker, D. Gammon and L. J. Sham, Nature 459, 1105 (2009). 
4. "Edge States in Graphene: from Gapped Flat Band to Gapless Chiral Modes", W. Yao, S.Y. Yang and Q. Niu, Phys. Rev. Lett., 102, 096801 (2009).
5. "Berry Phase Effects on the Exciton Transport and on the Exciton Bose-Einstein Condensate", W. Yao and Q. Niu, Phys. Rev. Lett., 101, 106401 (2008).
6. "Valley Contrasting Physics in Graphene: Magnetic Moment and Topological Transport", D. Xiao, W. Yao and Q. Niu, Phys. Rev. Lett., 99, 236809 (2007).
7. "Optical Control of Topological Quantum Transport in Semiconductors", W. Yao, A.H. MacDonald and Q. Niu, Phys. Rev. Lett., 99, 047401 (2007).
8. "Restoring Coherence Lost to a Slow Interacting Mesoscopic Spin Bath", Wang Yao, Ren-Bao Liu and L. J. Sham, Phys. Rev. Lett. 98, 077602 (2007).
9. "Theory of Electron Spin Decoherence by Interacting Nuclear Spins in a Quantum Dot", Wang Yao, Ren-Bao Liu and L. J. Sham, Phys. Rev. B 74, 195301 (2006).
10. "Theory of Control of the Spin-Photon Interface for Quantum Networks", Wang Yao, Ren-Bao Liu and L. J. Sham, Phys. Rev. Lett. 95, 030504 (2005).

Prof. F.C. Zhang

1. "Andreev and Single Particle Tunneling Spectroscopies in Underdoped Cuprates", K. Y. Yang, K. Huang, W. Q. Chen, T. M. Rice, F. C. Zhang, Phys. Rev. Lett. 105, 167004 (2010).
2. "Magnetoelectric Photocurrent Generated by Direct Interband Transitions in InGaAs/InAlAs Two-Dimensional Electron Gas", J. F. Dai, H. Z. Lu, C. L. Yang, S. Q. Shen, F. C. Zhang, X. D. Cui, Phys. Rev. Lett. 104, 246601 (2010).
3. "Anderson Impurity in a Helical Metal", X. Y. Feng, W. Q. Chen, J. H. Gao, Q. H. Wang, and F. C. Zhang, Phys. Rev. B 81, 235411 (2010).
4. "π-junction to Probe Antiphase s-wave Pairing in Iron Pnictide superconductors", W. Q. Chen, F. J. Ma, Z. Y. Lu, F. C. Zhang, Phys. Rev. Lett. 103, 207001 (2009).
5. "Strong Coupling Theory for Superconducting Iron Pnictides", W. Q. Chen, K. Y. Yang, Y. Zhou, F. C. Zhang, Phys. Rev. Lett. 102, 047006 (2009).
6. "Na₄Ir₃O₈ as a 3D Spin Liquid with Fermionic Spinons", Y. Zhou, P. A. Lee, T. K. Ng, F. C. Zhang, Phys. Rev. Lett. 101, 197201 (2008).
7. "Even Parity, Orbital Singlet and Spin Triplet Pairing for Superconducting La(O_1-xF_x)FeAs, X. Dai, Z. Fang, Y. Zhou, F. C. Zhang, Phys. Rev. Lett. 101, 057008 (2008).
8. "Influence of the Trap Shape on the SuperfluidMott Transition in Ultracold Atomic Gases", P.N. Ma, K.Y. Yang, L. Pollet, J.V. Porto, M. Troyer and F.C. Zhang, arXiv:0803.0546, accepted to be published in Physical Review B (2008).
9. "Quantum Oscillations in Magnetic Field Induced Antiferromagnetic Phase of Underdoped Cuprates: Application to Ortho-II YBa₂Cu₃O_6.5", W. Q. Chen, K. Y. Yang, T. M. Rice, F. C. Zhang, EPL 82, 17004 (2008).
10. "Resonant Intrinsic Spin Hall Effect in p-type GaAs Quantum Well Structure", X. Dai, Z. Fang, Y.G. Yao and F.C. Zhang, Physical Review Letters, 96, 086802 (2006).
11. "Phenomenological Theory of the Pseudogap State", K. Y. Yang, T. M. Rice, and F. C. Zhang, Phys. Rev. B 73, 174501 (2006).
12. "Particle-hole Asymmetry in Doped Mott Insulators: Implications for Tunneling and Photoemission Spectroscopics", M. Randeria, R. Sensarma, N. Trivedi, F. C. Zhang, Phys. Rev. Lett. 95, 137001 (2005).
13. "Gossamer Superconductivity near Antiferromagnetic Mott Insulator in Layered Organic Conductors", J. Y. Gan, Y. Chen, Z. B. Su, F. C. Zhang, Phys. Rev. Lett. 94, 067005 (2005).
14. "Resonant Spin Hall Conductance in Two-dimensional Electron Systems with a Rashba Interaction in a Perpendicular Magnetic Field", S. Q. Shen, M. Ma, X. C. Xie, and F. C. Zhang, Phys. Rev. Lett. 92, 256603 (2004).
15. "The Physics behind High-temperature Superconducting Cuprates: the "Plain Vanilla" Version of RVB", P. W. Anderson, P. A. Lee, M. Randeria, T. M. Rice, N. Trivedi, and F. C. Zhang, J. Phys.: Condense Matter 24, Topical Review R755 (2004).
16. "Gossamer Superconductor, Mott Insulator, and Resonating Valence Bond State in Correlated Electron Systems", F. C. Zhang, Phys. Rev. Lett. 90, 207002 (2003).
17. "Orbitally Degenerate Spin-1 Model for Insulating V₂O₃", F. Mila, H. Shiina, F. C. Zhang, A. Joshi, M. Ma, and T. M. Rice, Phys. Rev. Lett. 85, 1714 (2000).
18. "SU(4) Theory for Spin Systems with Orbital Degeneracy", Y. Q. Li, M. Ma, D. N. Shi, and F. C. Zhang, Phys. Rev. Lett. 81, 3527 (1998).
19. "Electronic Structure of Lanthanum Hydrides with Switchable Optical Properties", K. K. Ng, F. C. Zhang, V. I. Anisimov, and T. M. Rice, Phys. Rev. Lett. 78, 1311-1314 (1997).
20. "Momentum-dependent Charge Transfer Excitations in Sr₂CuO₂Cl₂-angle  Resolved Electron Energy Loss Spectroscopy", Y. Y. Wang, F. C. Zhang, V. P. Dravid, K. K. Ng, M. V. Klein, S. E. Schnatterly, and L. L. Miller, Phys. Rev. Lett. 77, 1809-1812 (1996).
21. "Superconductivity in Quasi-one-dimensional Spin Liquid", M. Sigrist, T. M. Rice, and F. C. Zhang, Phys. Rev. B 49, 12058-12061 (1994).
22. "Superconducting Instability of Staggered-flux Phase in the t-J Model", F. C. Zhang, Phys. Rev. Lett. 64, 974-977 (1990).
23. "A Renormalized Hamiltonian Approach to a Resonant Valence Bond Wavefunction", F. C. Zhang, C. Gros, T. M. Rice and H. Shiba, Superconductor Science and Technology Volume 1, 36-46 (1988).
24. "Effective Hamiltonian for the Superconducting Cu-oxides", F. C. Zhang and T. M. Rice, Phys. Rev. B 37, 3759-3761 (1988).
25. "Excitation Gap in the Fractional quantum effect: Finite layer thickness corrections", F. C. Zhang and S. Das Sarma, Phys. Rev. B 33 (Rapid Comm.), 2903-2905 (1986).
26. "Ground State of Two Dimensional Electrons and the Reversed Spins in the Fractional Quantum Hall Effect", F. C. Zhang and T. Chakraborty, Phys. Rev. B 30 (Rapid Comm.), 7320-7322 (1984).
27. "1/N Expansion for the Degenerate Anderson Model in the Mixed Valence Regime", F. C. Zhang and T. K. Lee, Phys. Rev. B 28, page 33-38 (1983).