Valley Dependent Optoelectronics from Inversion Symmetry Breaking

TL;DR

This paper explores how inversion symmetry breaking in materials like graphene causes valley-dependent optical properties, enabling new valley optoelectronic applications by linking optical transitions, orbital magnetic moments, and Berry curvatures.

Contribution

It reveals a universal connection between optical oscillator strength, orbital magnetic moment, and Berry curvature, providing a principle for optical measurement of magnetization and Hall conductivity.

Findings

Valley-dependent optical selection rules in graphene due to symmetry breaking

Universal link between optical transitions, magnetic moments, and Berry curvature

Potential for valley-based optoelectronic devices

Abstract

Inversion symmetry breaking allows contrasted circular dichroism in different k-space regions, which takes the extreme form of optical selection rules for interband transitions at high symmetry points. In materials where band-edges occur at noncentral valleys, this enables valley dependent interplay of electrons with light of different circular polarizations, in analogy to spin dependent optical activities in semiconductors. This discovery is in perfect harmony with the previous finding of valley contrasted Bloch band features of orbital magnetic moment and Berry curvatures from inversion symmetry breaking [Phys. Rev. Lett. 99, 236809 (2007)]. A universal connection is revealed between the k-resolved optical oscillator strength of interband transitions, the orbital magnetic moment and the Berry curvatures, which also provides a principle for optical measurement of orbital magnetization and intrinsic anomalous Hall conductivity in ferromagnetic systems. The general physics is demonstrated in graphene where inversion symmetry breaking leads to valley contrasted optical selection rule for interband transitions. We discuss graphene based valley optoelectronics applications where light polarization information can be interconverted with electronic information.