Title: Quantum Chemistry, correlation and topology in semiconductor moiré
Time: 3pm Nov. 29, 2021（Beijing time）
Speaker: Yang Zhang (MIT Physics)
Zoom Meeting ID: 972 5229 1543
Meeting URL: https://mit.zoom.us/j/97252291543
Abstract:
Transition metal dichalcogenide (TMD) based moiré materials have been shown to host various correlated electronic phenomena including Mott insulating states and fractional filling charge orders, quantum anomalous Hall and quantum spin Hall effect. To describe the low energy electronic states of long wavelength moiré superlattice, we introduced the concept of moiré quantum chemistry and developed the density functional theory to study the filling dependent insulating state and emergent magnetic properties [1,2]. In twisted homobilayer MoS2, we proposed the electrical tunable charge order and interaction induced Mott ferroelectricity [3].
More recently, we developed the theory of topological moiré bands in AB-stacked TMD hetorobilayers [4,5]. Valley contrasting Chern bands with non-trivial spin texture are formed from interlayer hybridization between moiré bands of nominally opposite spins. This work establishes a recipe for creating topological states in AB stacked TMD bilayers by tuning the displacement field, which provides a highly tunable platform for realizing quantum spin Hall and interaction induced quantum anomalous Hall effects. These series of work reveal rich physics of semiconductor moiré superlattices as manifested in a variety of correlated and topological states.
References:
[1] Y Zhang, N Yuan, L Fu, PRB 102 (20), 201115
[2] Y Zhang, H Isobe, L Fu, arXiv:2005.04238
[3] Y Zhang, T Liu, L Fu, PRB 103 (15), 155142
[4] Y Zhang, T Devakul, L Fu, PNAS 118 (36), 2021
[5] T Li, et al, Nature (in press)
About the speaker：
Yang Zhang is a postdoc associate in MIT Physics from April 2019. He obtained the Bachelor’s degree in Physics from the Tsinghua University, China in 2015 and PhD in Physics from the Max Planck Institute (Dresden, Germany) in 2019. He is mainly interested in transport and nonlinear optics in quantum materials, and the correlated and topological states in semiconductor moiré system.
