Observation of Quantum Hall Valley Skyrmions

TL;DR

This study observes valley Skyrmions in a quantum Hall system by tuning valley energies with strain, revealing interaction effects that differ from single-particle predictions in a 2D electron system.

Contribution

It provides experimental evidence for valley Skyrmions in a quantum Hall regime, highlighting the role of interactions in multi-valley systems.

Findings

Finite energy gap at zero strain

Rapid increase of gap with strain beyond single-particle expectations

Identification of valley Skyrmions as lowest energy excitations

Abstract

We report measurements of the interaction-induced quantum Hall effect in a spin-polarized AlAs two-dimensional electron system where the electrons occupy two in-plane conduction band valleys. Via the application of in-plane strain, we tune the energies of these valleys and measure the energy gap of the quantum Hall state at filling factor $\nu$ = 1. The gap has a finite value even at zero strain and, with strain, rises much faster than expected from a single-particle picture, suggesting that the lowest energy charged excitations at $\nu=1$ are "valley Skyrmions".