Twisted bilayer graphene is highly sensitive to external perturbations. Strains, and the presence of the substrate, break the symmetries of the central bands. The resulting changes in the Berry curvature lead to valley currents and to a nonlinear Hall effect. We show that these effects, described by a Berry dipole, can be very significant, such that the nonlinear effects surpass the linear response for moderate applied fields, ∼0.1mV/μm. The dependence of these effects on applied strain, coupling to the substrate, density of carriers, and temperature, makes them highly tunable.
|Original language||English (US)|
|Journal||Physical Review B|
|State||Published - May 3 2021|
Bibliographical noteFunding Information:
Acknowledgments. P.A.P. and F.G. acknowledge funding from the European Commission, under the Graphene Flagship, Core 3, Grant No. 881603, and from grants NMAT2D (Comunidad de Madrid, Spain) and SprQuMat and SEV-2016-0686 (Ministerio de Ciencia e Innovación, Spain). T.L. acknowledges support from the National Science Foundation under Grant No. NSF/EFRI-1741660.
© 2021 American Physical Society.