Shubnikov-de Haas oscillations of high mobility holes in monolayer and bilayer WSe$_2$: Landau level degeneracy, effective mass, and negative compressibility

TL;DR

This study investigates the magnetotransport properties of high mobility holes in monolayer and bilayer WSe$_2$, revealing Landau level degeneracy, subband structure, and negative compressibility through analysis of Shubnikov-de Haas oscillations and quantum Hall states.

Contribution

It provides detailed characterization of Landau level degeneracy, effective mass, and subband structure in monolayer and bilayer WSe$_2$, highlighting negative compressibility effects.

Findings

Landau level degeneracy is predominantly two-fold in both monolayer and bilayer WSe$_2$

Fourier analysis reveals two subbands in bilayer WSe$_2$

Effective hole mass is approximately 0.45 times the electron mass

Abstract

We study the magnetotransport properties of high mobility holes in monolayer and bilayer WSe$_2$, which display well defined Shubnikov-de Haas (SdH) oscillations, and quantum Hall states (QHSs) in high magnetic fields. In both mono and bilayer WSe$_2$, the SdH oscillations and the QHSs occur predominantly at even filling factors, evincing a two-fold Landau level degeneracy. The Fourier transform analysis of the SdH oscillations in bilayer WSe$_2$ reveal the presence of two subbands localized in the top or the bottom layer, as well as negative compressibility. From the temperature dependence of the SdH oscillations we determine a hole effective mass of $0.45m_{0}$ for both mono and bilayer WSe$_2$.