Valley-Filling Instability and Critical Magnetic Field for Interaction-Enhanced Zeeman Response in Doped WSe$_2$ Monolayers

TL;DR

This paper develops an extit{ab initio} method to compute interaction-enhanced g-factors in doped WSe$_2$ monolayers, revealing a critical magnetic field where valley-filling instability occurs, relevant for quantum phase transitions and valleytronics.

Contribution

The paper introduces a first-principles approach to calculate many-body interaction effects on g-factors in doped TMD monolayers, linking them to valley-filling instabilities.

Findings

Enhanced g-factors due to screened exchange interactions

Existence of a critical magnetic field $B_c$ where enhancement vanishes

Identification of conditions leading to valley-filling instability

Abstract

Carrier-doped transition metal dichalcogenide (TMD) monolayers are of great interest in valleytronics due to the large Zeeman response (g-factors) in these spin-valley-locked materials, arising from many-body interactions. We develop an \textit{ab initio} approach based on many-body perturbation theory to compute the interaction-enhanced g-factors in carrier-doped materials. We show that the g-factors of doped WSe$_2$ monolayers are enhanced by screened exchange interactions resulting from magnetic-field-induced changes in band occupancies. Our interaction-enhanced g-factors $g^*$ agree well with experiment. Unlike traditional valleytronic materials such as silicon, the enhancement in g-factor vanishes beyond a critical magnetic field $B_c$ achievable in standard laboratories. We identify ranges of $g^*$ for which this change in g-factor at $B_c$ leads to a valley-filling instability and Landau level alignment, which is important for the study of quantum phase transitions in doped TMDs. We further demonstrate how to tune the g-factors and optimize the valley-polarization for the valley Hall effect.