Berry curvature dipole senses topological transition in a moiré superlattice

Berry curvature dipole senses topological transition in a moiré superlattice

“…The experimental data used in the figures of the main text are available in Zenodo with the identifier doi:10.5281/zenodo.5211285 [42]. Additional data related to this study are available from the corresponding authors upon reasonable request.…”

Nonlinear anomalous Hall effects probe topological phase-transitions in twisted double bilayer graphene

“…We particularly focus on the perpendicular electric field tunability and strain induced symmetry reductions of the TDBG which play pivotal roles in generating NLA Hall effects in TDBG. We emphasize that a perpendicular electric field can be experimentally applied in a specially designed field-effect-transistor like device structure with dual gates [13][14][15] . Strain, on the other hand, generally appears in 2D systems during fabrication on a substrate and is ubiquitous in almost every moiré platform 56 .…”

“…By studying the scaling of total NLA Hall response with the Drude conductivity, the BCD dependent contributions can be extracted from the total NLA Hall response. In particular, the perpendicular electric field provides a useful knob to vary the conductivity at a fixed temperature to study the scaling in TDBG and detect topological transition from the sign-reversal of BCD 15 . A fixed temperature ensures that the scaling parameters are not tuned with temperature 66 and helps in accurate estimation of BCD.…”

“…For very small twist angles, the enhanced impact of electron-electron interactions due to narrow bandwidth enables a rich phase diagram of correlated phases in TBG [2][3][4][5] . In addition to TBG, other stacked moiré systems such as twisted double bilayer graphene (TDBG) [6][7][8][9][10][11][12][13][14][15] , twisted trilayer graphene [16][17][18][19] , and marginally twisted transition metal dichalcogenides [20][21][22] also show fascinating strong correlation effects. Moiré systems also offer a promising platform for exploring the valley and topological physics.…”

“…Moiré systems also offer a promising platform for exploring the valley and topological physics. In addition to large Berry curvature hotspots, valley-Chern number based topological phase transitions 23 have also been demonstrated in moiré systems such as TBG 24 , TDBG 10,15,[25][26][27][28][29] , multi-layered twisted systems 30,31 , and twisted transition metal dichalcogenides 32,33 .…”