Optical Detection and Manipulation of Pseudospin Orders in Wigner Crystals

TL;DR

This paper demonstrates how optical methods can detect and manipulate pseudospin orders in Wigner crystals by exploiting their coupling to orbital vibrations, revealing new ways to study and control quantum states.

Contribution

It introduces a novel optical detection technique for pseudospin orders in Wigner crystals through terahertz conductivity signatures and shows how optical drives can induce phase transitions.

Findings

Optical signatures of pseudospin order are identified in terahertz conductivity.

Antiferromagnetic pseudospin order produces characteristic absorption peaks.

Strong optical drives can induce phase transitions to stripe antiferromagnetic states.

Abstract

In Wigner-crystal states of two-dimensional electrons, the spin ordering remains poorly understood. The small energy differences between candidate spin orders make theoretical studies less reliable, and probing magnetic order at a nonzero wave vector is experimentally challenging. In modern realizations of Wigner crystals, the electronic spin degree of freedom is often replaced by a valley pseudospin associated with nonzero Berry curvature. The resulting anomalous velocity couples the electrons' pseudospin texture to their orbital vibration. We show that this mechanism enables optical detection of pseudospin orders in Wigner crystals by producing sharp signatures in the terahertz optical conductivity. For example, antiferromagnetic pseudospin order enables light to excite collective electronic vibrations at the ordering wave vector, generating a characteristic absorption peak. Based on the same principle, we further show that a strong optical drive generates an effective potential that reshapes the pseudospin energy landscape, inducing phase transitions to stripe antiferromagnetic states. These results point to a route for optical detection and control of spin order via its coupling to orbital motion.