Berry Curvature-Driven Valley Nernst Effect in Monolayer WSe₂.

Abstract

The Berry curvature in a Dirac cone causes anomalous transport phenomena, including anomalous Hall, anomalous Nernst, and Valley Hall effects. Detecting the Berry curvature in a 2D transition metal dichalcogenide (TMD) layer requires breaking time-reversal symmetry to create a population imbalance between the K⁺ and K^- valleys. Direct observation and control of valley polarization in a 2D TMD layer remain challenging, especially for practical applications. Here, we present the first experimental verification of the Berry curvature-driven valley Nernst effect (VNE) in interlayer TMDs, focusing on the monolayer (ML) WSe₂ in a Pt/YIG bilayer structure. Experiments and calculations show that our VNE signals result from the high Berry curvature of the ML WSe₂ layer. This opens up a new way to generate spin- and valley-current-based thermoelectric devices.