Theory of the strain-induced magnetoelectric effect in planar Dirac systems

Abstract

The magnetoelectric response in inversion-breaking two-dimensional Dirac systems induced by strain is analyzed. It is shown that, in the same way that the piezoelectric response in these materials is related to the valley Chern number, the magnetic field and strain-induced electric polarization is related to the nontrivial Berry curvature and the derivative of the orbital magnetic moment per valley. We also show that the elastic vector field Ael present in these systems drives the system out of equilibrium in presence of a magnetic field, allowing for such electrical response. In contrast, we show that the strain plays a very different role in the generation of a nonequilibrium magnetization and optical activity. In this case, it is the modification of the band structure induced by strain that allows for the magnetic response to external electric perturbations.