Nonlinear nonreciprocal electronic conductivity driven by magnetic field gradients

TL;DR

This paper predicts that applying a spatially gradient magnetic field to centrosymmetric paramagnetic materials can induce nonlinear nonreciprocal electronic conductivity due to magnetic toroidal dipole moments, with potential experimental realization.

Contribution

It introduces a theoretical mechanism for nonlinear nonreciprocal conductivity driven by magnetic field gradients in centrosymmetric systems, highlighting the role of magnetic toroidal dipoles and antisymmetric spin-orbit interactions.

Findings

Magnetic field gradients induce magnetic toroidal dipoles breaking symmetries.

Effective coupling leads to nonlinear nonreciprocal transport.

Proposed experimental setup for observing effects.

Abstract

We theoretically propose the emergence of nonlinear nonreciprocal conductivity in centrosymmetric paramagnetic systems when a spatially gradient magnetic field is externally applied. The key essence lies in the appearance of magnetic toroidal dipole moment under the gradient field that breaks both spatial inversion and time-reversal symmetries. By analyzing a minimal tight-binding model on a two-dimensional system, we show that an effective coupling between the magnetic toroidal dipole moment arising from the gradient field and sublattice-dependent antisymmetric spin-orbit interaction plays an important role in inducing the nonlinear nonreciprocal transport. We also discuss the favorable situation to observe the nonlinear nonreciprocal conductivity in real materials by presenting an experimental setup in order to stimulate the findings.