Work Package A: Task 2

Theoretical description of non-linear phenomena induced by the topologically nontrivial band structure in selected 2D systems.

The non-linear Hall effect gives the possibility to get the information about the Berry curvature in nonmagnetic materials, and therefore about the topology of band structure directly from electrical measurements. In general, the non-linear Hall effect is not only a consequence of the dipole moment Berry curvature but also of the disorder scattering.

We will study the non-linear Hall effect under different external perturbations that lead to its origin, or modify the topological contribution. We aim to investigate the non-linear system responses, such as non-linear spin, valley Hall effects (charge, spin, valley), and other transport phenomena, for which the second-order response may be relevant. Moreover, the adequate theoretical description of non-linear system responses is also extremally important in the context of ultra-fast phenomena, where the system is far away from the equilibrium state. In such a case, the kinetic and dynamic properties of quasiparticles are out of the applicability of linear response formalism.