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

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 $g^{\ast }$ 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 $g^{\ast }$ 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.

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• Proximity-enhanced valley Zeeman splitting at the WS${}_2$/graphene interface
• Energy shifts and broadening of excitonic resonances in electrostatically-doped semiconductors