Eccentricity valley Hall effect

TL;DR

This paper introduces a novel eccentricity valley Hall effect in valleytronics, where the valley Hall angle depends on the geometric eccentricity of the Fermi surface, expanding the understanding of valley Hall phenomena.

Contribution

It reveals a new type of valley Hall effect in time-reversal-invariant valleys, governed by Fermi surface eccentricity, and demonstrates its universality and robustness in 2D materials.

Findings

Eccentricity VHE is governed by Fermi surface eccentricity.

Predicted a valley Hall angle of 0.74 in monolayer GeS2.

Effect detectable via nonlocal transport measurements.

Abstract

Valleytronics harnesses the valley degree of freedom -- energy-degenerate extrema in the electronic band structure -- for information storage and processing. Valley Hall effect (VHE) is a cornerstone of valleytronics, enabling electric generation of pure valley currents. While extensively studied in systems with valleys located at time-reversal-breaking points, here, we shift the paradigm to valleytronic platforms with time-reversal-invariant valleys (TRIVs), revealing a novel phenomenon: eccentricity VHE. Unlike conventional VHE, the valley Hall angle for eccentricity VHE is an intrinsic geometric property, governed solely by the eccentricity of the valley Fermi surface, rendering it highly robust against variations in temperature or carrier density. Eccentricity VHE emerges universally across all 25 layer groups supporting TRIVs. We demonstrate these distinctive features in monolayer GeS$_{2}$ via first-principles calculations, predicting a significant valley Hall angle of 0.74. This effect can be detected through nonlocal transport measurements exhibiting characteristic scaling behavior, or, in certain cases, through valley-layer coupling. Our findings reveal a critical overlooked facet of valley Hall physics, transcend the established VHE paradigm, and significantly broadens the scope of valleytronics.