WSe2/WS2 moir\'e superlattices: a new Hubbard model simulator
Abstract
The Hubbard model, first formulated by physicist John Hubbard in the 1960s, is a simple theoretical model of interacting quantum particles in a lattice. The model is thought to capture the essential physics of high-temperature superconductors, magnetic insulators, and other complex emergent quantum many-body ground states. Although the Hubbard model is greatly simplified as a representation of most real materials, it has nevertheless proved difficult to solve accurately except in the one-dimensional case. Physical realization of the Hubbard model in two or three dimensions, which can act as quantum simulators, therefore have a vital role to play in solving the strong-correlation puzzle. Here we obtain a quantum phase diagram of the two-dimensional triangular lattice Hubbard model by studying angle-aligned WSe2/WS2 bilayers, which form moir\'e superlattices because of the difference in lattice constant between the two two-dimensional materials. We probe both charge and magnetic properties of the system by measuring the dependence of optical response on out-of-plane magnetic field, and on gate-tuned carrier density. At half filling of the first hole moir\'e superlattice band, we observe a Mott insulating state with antiferromagnetic Curie-Weiss behavior as expected for a Hubbard model in the strong interaction regime. Past half filling, our experiment suggests an antiferromagnetic to paramagnetic quantum phase transition near 0.6 filling. Our results establish a new solid-state platform based on moir\'e superlattices which can be used to simulate outstanding problems in strong correlation physics that are manifested by triangular lattice Hubbard models.
Cite
@article{arxiv.1910.08673,
title = {WSe2/WS2 moir\'e superlattices: a new Hubbard model simulator},
author = {Yanhao Tang and Lizhong Li and Tingxin Li and Yang Xu and Song Liu and Katayun Barmak and Kenji Watanabe and Takashi Taniguchi and Allan H MacDonald and Jie Shan and Kin Fai Mak},
journal= {arXiv preprint arXiv:1910.08673},
year = {2019}
}