Theory of nonlinear response for charge and spin currents

Zhi-Fan Zhang, Zhen-Gang Zhu, and Gang Su 

Physical Review B 104, 115140 (2021)-Published 21 September 2021


The nonlinear Hall effect, which is the second-order harmonic charge Hall effect from the Berry curvature dipole in momentum space, has received much attention recently. As the responses to higher harmonics of the driving ac electric fifield are prominent and measurable, we develop a general nonlinear theory by taking the charge and spin currents as well as the longitudinal and transverse effects into account. We introduce the expansion order of the electric fifield and Berry curvature multipole moment, where the Berry curvature dipole is a particular one manifesting itself at the second harmonic order and the second expansion order of the electric fifield. There are four cases with conserving or breaking the time-reversal symmetry (TRS) and inversion symmetry (IS). We fifind a specifific “selection rule” that only longitudinal odd harmonic order charge currents exist for conserving both the TRS and IS, and with breaking both symmetries, all harmonic order charge and spin currents are nonzero. With conserving TRS and breaking IS, the charge Hall current exists at even harmonic order, and the longitudinal charge current occurs at odd harmonic order. Only the longitudinal spin current survives at even harmonic order. With breaking TRS and conserving IS, only odd harmonic order charge and spin currents can appear. Moreover, we observe that every harmonic order current contains a series of infifinite-order expansion of the electric fifield. We further show that the Berry curvature dipole and quadrupole can be determined by measuring the second and fourth harmonic order currents in experiments. This may open a way to explore the higher responses of an ac driving system.