ABSTRACT
Moiré superlattices form in van der Waals bilayers with a small lattice mismatch or misalignment. I will present theoretical proposals of using moiré bilayers as a quantum simulation platform to realize model Hamiltonians. In semiconducting transition metal dichalcogenide (TMD) heterobilayers, isolated flat moiré bands can be used to simulate Fermi-Hubbard model on a triangular lattice, in which parameters such as bandwidth, interaction strength, and band filling are widely tunable [1]. When the two layers are formed from the same TMD, holes in ±K valleys move in a layer-pseudospin skyrmion texture in real space. The low-energy moiré bands can be mapped to the quantum-spin-Hall Kane-Mele model for suitable model parameters [2].
In the past two years, several experimental works that follow closely the above theoretical proposals have been reported. A recent experiment [3] reports the observation of quantum anomalous Hall effect in AB-stacked MoTe2/WSe2. This experiment is a surprise, as it realizes topological states in a heterobilayer instead of the theoretically proposed homobilayer. I will discuss how this experiment could be understood theoretically and highlight the interplay between single-particle band topology and many-body interaction.
References
[1] F. Wu,et al., Phys. Rev. Lett. 121, 026402 (2018).
[2] F. Wu,et al., Phys. Rev. Lett. 122, 086402 (2019).
[3] T. Li, et al., arXiv:2107.01796.
BIOGRAPHY
Fengcheng Wu is a Professor in the School of Physics and Technology at Wuhan University. He received his BSc in Physics from University of Science and Technology of China in 2011 and PhD in physics from University of Texas at Austin in 2016. He performed postdoc research at Argonne National Laboratory (2016-2018) and University of Maryland (2018-2020). His research is on condensed matter theory, with a focus on low-dimensional quantum physics. He made a number of theoretical predictions for physics in moiré superlattices, which have recently been experimentally realized/observed. These predictions include: (1) proposal of using semiconductor moiré bilayers as quantum simulators; (2) prediction of topological phases in semiconductor moiré bilayers; (3) prediction of signatures of moiré excitons in optical spectrum; (4) prediction of phonon-induced giant T-linear resistivity in graphene moiré systems.
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