C. ORTIX: Non-linear and anomalous planar Hall effect in Dirac materials

It has been recently established that Hall-like transverse currents can appear as a second-order response to an external electric field in a wide class of time-reversal symmetric and inversion-symmetry broken materials [1]. This non-linear Hall effect possesses a quantum contribution directly arising from the dipole moment of the Berry curvature, and has been recently observed in two-dimensional materials with strong spin-orbit coupling where the low-energy Dirac quasiparticles form tilted Dirac cones.

I will show that this topological effect can appear even in absence of spin-orbit coupling [2]. In such systems, it is the warping of the Fermi surface that triggers sizeable Berry curvature dipoles. As a prominent example, I will show that uniaxially strained bilayer graphene with gate-induced bandgaps has dipoles comparable in strength to those observed in bilayer transition metal dichalcogenides [3]. In the second part of the talk, I will show that the Berry curvature in two-dimensional trigonal crystals can yield an anomalous  planar Hall effect [4] producing a transverse current even in a configuration where the driving electric field is aligned with the external magnetic field.

[1] C. Ortix, Advanced Quantum Technologies 2100056 (2021).
[2] R. Battilomo, N. Scopigno, C. Ortix, PRL 123, 196403 (2019).
[3] S.-C. Ho, …, C. Ortix, T.-M. Chen, Nature Electronics 4, 116 (2021).
[4] R. Battilomo, N. Scopigno, C. Ortix, Phys.Rev.Research 3, L012006(2021)