Theory of electric polarization in multi-orbital Mott insulators

TL;DR

This paper presents a theoretical framework for understanding how electric fields interact with spins in multi-orbital Mott insulators, revealing a universal coupling mechanism that influences spin dynamics and excitations.

Contribution

It introduces a generic, non-relativistic dynamical coupling mechanism between electric fields and spins, applicable to all crystal lattices, based on the Berry phase of electrons.

Findings

Discovery of a universal electric-spin coupling mechanism

Prediction of electric-field-induced electron spin resonance

Analysis of electric field effects on spin textures and magnetic excitations

Abstract

The interaction between the electric field, E, and spins in multi-orbital Mott insulators is studied theoretically. We find a generic dynamical coupling mechanism, which works for all crystal lattices and which does not involve relativistic effects. The general form of the coupling is -T_ab E_a e_b, where e is the `internal' electric field originating from the dynamical Berry phase of electrons and T_ab is a tensor determined by lattice symmetry. We discuss several effects of this interaction: (i) an unusual electron spin resonance induced by an oscillating electric field, (ii) the displacement of spin textures in an applied electric field, and (iii) the resonant absorption of circularly polarized light by Skyrmions, magnetic bubbles, and magnetic vortices.