Abstract
Moire transition metal dichalcogenides have served as a versatile platform for simulating Hubbard physics. Recent experiments have identified robust superconductivity in moire bilayer WSe2 for certain twist angles. Here, we propose the gossamer nature of the superconductivity recently discovered at half-filling and zero displacement field in twisted WSe2. By mapping the moire continuum system to an effective extended single-orbital Hubbard model on the triangular lattice, we employ renormalized mean-field theory to investigate the strong coupling phase diagram. We find that a moderate Coulomb repulsion partially suppresses charge fluctuations while preserving a finite density of mobile doublons and holes. In this regime, the interplay between extended kinetic hoppings and antiferromagnetic superexchange stabilizes a chiral d + id superconducting phase. Our results naturally account for the twist-angle-dependent evolution from a Mott insulator to a superconductor and eventually to a correlated metal. Furthermore, the model demonstrates that this half-filled pairing state vanishes rapidly upon density doping, consistent with experimental observations.
Biography
Prof. Zhang is a condensed matter theorist, specializing unconventional superconductivity and other strongly correlated electron systems. He did his college education in Fudan Univ, Shanghai, and received Ph.D. in physics at Virginia Tech in 1983. He was a postdoc fellow in Univ. of Minnesota, Univ. of Maryland, and ETH-Zurich 1983-1988, before he joined Univ. of Cincinnati, Ohio as a faculty. He moved to University of Hong Kong as Chair of Physics in 2003, and was the Head of Physics Dept for several years. Zhang joined Zhejiang Univ. in China in 2014, and has been Director of Kavli Inst. of Theoretical Science at the Univ. of Chinese Academy of Sciences since 2017.
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