Tunable Valley Polarization and Valley Orbital Magnetic Moment Hall Effect in Honeycomb Systems with Broken Inversion Symmetry

TL;DR

This paper demonstrates a method to achieve tunable valley polarization in honeycomb systems with broken inversion symmetry, revealing a novel valley orbital magnetic moment Hall effect driven by Berry curvature differences.

Contribution

It introduces elliptical pumping as an effective way to generate valley polarization and predicts a new valley orbital magnetic moment Hall effect in MX2 monolayers.

Findings

Elliptical pumping enhances valley polarization compared to circular pumping.

A valley orbital magnetic moment Hall effect is predicted without charge current.

The effect is tunable and can obscure the spin Hall effect.

Abstract

In this Letter, a tunable valley polarization is investigated for honeycomb systems with broken inversion symmetry such as transition-metal dichalcogenide MX2 (M = Mo, W; X = S, Se) monolayers through elliptical pumping. As compared to circular pumping, elliptical pumping is more universal and effective method to create coherent valley polarization. When two valleys of MX2 monolayers are doped or polarized, a novel anomalous valley orbital magnetic moment Hall effect driven by opposite Berry curvatures at different valleys is predicted and can generate orbital magnetic moment current without the accompaniment of a charge current, opening a new avenue for exploration of valleytronics and orbitronics. Valley orbital magnetic moment Hall effect is expected to obscure spin Hall effect and is tunable under elliptical pumping.