Tunable $\Gamma - K$ Valley Populations in Hole-Doped Trilayer WSe$_2$

TL;DR

This study combines experiments and theory to show how electric fields can tune valley populations in trilayer WSe$_2$, revealing distinct subband behaviors and effective masses in the material's valence bands.

Contribution

It provides the first detailed analysis of how transverse electric fields influence valley populations and subband characteristics in trilayer WSe$_2$.

Findings

Valence holes occupy two subbands associated with $K$ and $\Gamma$ valleys.

Electric field transfers holes from $\Gamma$ to $K$ orbitals.

Different effective masses for $K$ and $\Gamma$ valley holes.

Abstract

We present a combined experimental and theoretical study of valley populations in the valence bands of trilayer WSe$_2$. Shubnikov$-$de Haas oscillations show that trilayer holes populate two distinct subbands associated with the $K$ and $\Gamma$ valleys, with effective masses 0.5$m_e$ and $1.2m_e$, respectively; $m_e$ is the bare electron mass. At a fixed total hole density, an applied transverse electric field transfers holes from $\Gamma$ orbitals to $K$ orbitals. We are able to explain this behavior in terms of the larger layer polarizability of the $K$ orbital subband.