Abstract
Recent studies have shown that moiré flat bands in twisted bilayer graphene (TBG) can acquire nontrivial Berry curvatures when aligned with a hexagonal boron nitride substrate, which can be manifested as a correlated Chern insulator near the 3/4 filling. In this Letter, we show that the large Berry curvatures in the moiré bands lead to a strong nonlinear Hall (NLH) effect in strained TBG with general filling factors. Under a weak uniaxial strain ∼0.1%, the Berry curvature dipole which characterizes the nonlinear Hall response can be as large as ∼200Å, exceeding the values of previously known nonlinear Hall materials by two orders of magnitude. The dependence of the giant NLH effect as a function of electric gating, strain, and twist angle is further investigated systematically. Importantly, we point out that the giant NLH effect appears generically for a twist angle near the magic angle due to the strong susceptibility of nearly flat moiré bands to symmetry breaking induced by strains, which can even induce a topological band inversion. Our results establish TBG as a promising platform for investigating nonlinear effects such as the NLH effect, the nonlinear Nernst effect, and the nonlinear thermal Hall effect due to its giant Berry curvature dipole.
Original language | English |
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Article number | L041111 |
Number of pages | 6 |
Journal | Physical Review B |
Volume | 106 |
Issue number | 4 |
DOIs | |
State | Published - 15 Jul 2022 |
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics