Nonlinear response in strongly correlated systems

Nonlinear responses in condensed matter are intensively studied because they provide rich information about materials and hold the possibility of being applied in diodes or high-frequency optical devices [1-4]. While nonlinear responses in noninteracting models have been explored widely, the effect of strong correlations on the nonlinear response is still poorly understood.
This talk will introduce a Green's function method to calculate nonlinear conductivities in strongly correlated materials [5-6]. Correlation effects are thereby included by the self-energy of the material. I will then use this method to study the nonlinear conductivities in noncentrosymmetric f-electron systems. The first system is a heavy Fermion system, where a nonreciprocal conductivity appears in the ferromagnetic phase. The nonreciprocal conductivity thereby always occurs perpendicular to the magnetization of the system and has a strong spin dependence, which might be advantageous for spintronic applications. The second system is a model corresponding to the Weyl-Kondo semimetal Ce3Bi4Pd3, in which a giant spontaneous Hall effect without time-reversal symmetry breaking has been observed [7]. This Hall effect can be explained as a nonlinear Hall effect in an inversion-symmetry broken Weyl-semimetal. It has been shown that the nonlinear Hall effect is related to the Berry curvature dipole [4]. Our study shows that the magnitude of the experimentally observed nonlinear Hall effect can be explained by the strong correlations inherent in this f-electron material [8].

*Detailed information about the seminar refer to the email.