Pseudo-spin order of Wigner crystals in multi-valley electron gases

TL;DR

This paper investigates the pseudo-spin order in Wigner crystals formed in multi-valley electron gases at low densities, revealing various ordered phases influenced by material symmetries and parameters, with implications for recent experimental systems.

Contribution

It introduces a theoretical framework for understanding pseudo-spin ordering in Wigner crystals across different materials and predicts new electronic liquid crystalline phases.

Findings

Identification of striped and chiral pseudo-spin antiferromagnetic phases

Discovery of time-reversal symmetry breaking orbital loop-current order

Relevance to Wigner crystals in AlAs and transition metal dichalcogenides

Abstract

We study multi-valley electron gases in the low density ($r_s \gg 1$) limit. Here the ground-state is always a Wigner crystal (WC), with additional pseudo-spin order where the pseudo-spins are related to valley occupancies. Depending on the symmetries of the host semiconductor and the values of the parameters such as the anisotropy of the effective mass tensors, we find a striped or chiral pseudo-spin antiferromagnet, or a time-reversal symmetry breaking orbital loop-current ordered pseudo-spin ferromagnet. Our theory applies to the recently-discovered WC states in AlAs and in mono and bilayer transition metal dichalcogenides. We identify a set of interesting electronic liquid crystalline phases that could arise by continuous quantum melting of such WCs.