Evidence for an Anisotropic State of Two-Dimensional Electrons in High Landau Levels

TL;DR

This paper reports experimental evidence of anisotropic electronic states in high Landau levels of two-dimensional electron gases, observed through magneto-transport anomalies at very low temperatures, suggesting a spontaneous many-electron state.

Contribution

It provides experimental evidence for an anisotropic state in high Landau levels, highlighting temperature-dependent resistivity anomalies in 2D electron gases.

Findings

Anisotropic resistivity appears below 150mK in high Landau levels.

Anomalies are absent in lower Landau levels.

Phenomena suggest a spontaneous anisotropic many-electron state.

Abstract

Magneto-transport experiments on high mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures have revealed striking anomalies near half-filling of several spin-resolved, yet highly excited, Landau levels. These anomalies include strong anisotropies and non-linearities of the longitudinal resistivity rho_xx which commence only below about 150mK. These phenomena are not seen in the ground or first excited Landau level but begin abruptly in the third level. Although their origin remains unclear, we speculate that they reflect the spontaneous development of a generic anisotropic many-electron state.