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arXiv · 2008.02374

Spontaneous valley polarization of interacting carriers in a monolayer semiconductor

Jing Li·Mateusz Goryca·Nathan P. Wilson·Andreas V. Stier·Xiaodong Xu·Scott A. Crooker
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Abstract

We report magneto-absorption spectroscopy of gated WSe$_2$ monolayers in high magnetic fields up to 60~T. When doped with a 2D Fermi sea of mobile holes, well-resolved sequences of optical transitions are observed in both $\sigma^\pm$ circular polarizations, which unambiguously and separately indicate the number of filled Landau levels (LLs) in both $K$ and $K'$ valleys. This reveals the interaction-enhanced valley Zeeman energy, which is found to be highly tunable with hole density $p$. We exploit this tunability to align the LLs in $K$ and $K'$, and find that the 2D hole gas becomes unstable against small changes in LL filling and can spontaneously valley-polarize. These results cannot be understood within a single-particle picture, highlighting the importance of exchange interactions in determining the ground state of 2D carriers in monolayer semiconductors.

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Jing Li, Mateusz Goryca, Nathan P. Wilson, Andreas V. Stier, Xiaodong Xu, Scott A. Crooker. 2020-08-05. Spontaneous valley polarization of interacting carriers in a monolayer semiconductor. https://doi.org/10.1103/physrevlett.125.147602

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