Current-Induced Anisotropy and Reordering of the Electron Liquid-Crystal Phases in a Two-Dimensional Electron System

Abstract

The correlated phases in a two-dimensional electron system with a high index partially filled Landau level are studied in transport under nonequilibrium conditions by imposing a dc-current drive. At filling 1/4 and 3/4 of these Landau levels, where the charge density wave picture predicts an isotropic bubble phase, the dc drive induces anisotropic transport behavior consistent with stripe order. The easy axis of the emerging anisotropic phase is perpendicular to the drive. At half filling the anisotropic stripe phase is stabilized by the dc drive provided drive and easy-axis directions coincide.

Acoustic measurements of the stripe and the bubble quantum Hall phase

“…The 2DES has an electron density of × − 2.7 10 cm 11 2 . The shape of the 2DES, the 'mesa' is similar to a van-der-Pauw geometry which allows standard resistance measurements in the two crystal directions [29]. The SAW are launched from the etched surface with negligible back reflection at the 120 nm high mesa edge because of the long wavelength.…”

Anisotropic sliding dynamics, peak effect, and metastability in stripe systems

“…The alignment of the stripes in the 2DEG systems may be due to small intrinsic biases that form during sample growth 26 . There have also been recent 2DEG experiments that show that dc drives or other external driving can dynamically orient the stripes under certain conditions 27,28 . Other recent experiments have shown that the stripe direction can be controlled with a strain, making it possible to alter the anisotropy with a strain field 29 .…”

“…Other recent experiments have shown that the stripe direction can be controlled with a strain, making it possible to alter the anisotropy with a strain field 29 . Transport experiments in 2DEGs have revealed sharp conduction thresholds, a series of intricate jumps in the current versus resistance curves, pronounced hysteresis, and changes in the conduction noise, suggesting that these systems are undergoing depinning transitions and dynamic changes in the sliding dynamics 27,30,31 . Additional evidence for charge ordered states in 2DEGs has come from resonance measurements 32,33 .…”

Spin and Charge Ordering in the Quantum Hall Regime

“…The clear response of the bubble and stripe phases further allowed clarifying the impact of a strong unidirectional current flow on the stripe phase order. While in resistively detected transport measurements the stripe order appears to be strongly influenced when driving a large current perpendicular to the equilibrium stripe orientation [219], such an effect is conspicuously absent in the SAW measurement. This observation identifies the influence of an external current on the stripe orientation to be purely local.…”