Evidence for a fractional quantum Hall state with anisotropic longitudinal transport

TL;DR

This paper reports the discovery of a fractional quantum Hall state in the N=1 Landau level that exhibits both quantized Hall conductance and anisotropic longitudinal resistance, indicating a novel phase with broken rotational symmetry.

Contribution

The study presents evidence for a new fractional quantum Hall state with anisotropic transport properties in the N=1 Landau level, combining features of liquid and stripe phases.

Findings

Observation of a fractional quantum Hall plateau in N=1 LL

Simultaneous anisotropic longitudinal resistance

Evidence of a new phase with broken rotational symmetry

Abstract

At high magnetic fields, where the Fermi level lies in the N=0 lowest Landau level (LL), a clean two-dimensional electron system (2DES) exhibits numerous incompressible liquid phases which display the fractional quantized Hall effect (FQHE) (Das Sarma and Pinczuk, 1997). These liquid phases do not break rotational symmetry, exhibiting resistivities which are isotropic in the plane. In contrast, at lower fields, when the Fermi level lies in the $N\ge2$ third and several higher LLs, the 2DES displays a distinctly different class of collective states. In particular, near half filling of these high LLs the 2DES exhibits a strongly anisotropic longitudinal resistance at low temperatures (Lilly et al., 1999; Du et al., 1999). These "stripe" phases, which do not exhibit the quantized Hall effect, resemble nematic liquid crystals, possessing broken rotational symmetry and orientational order (Koulakov et al., 1996; Fogler et al., 1996; Moessner and Chalker, 1996; Fradkin and Kivelson, 1999; Fradkin et al, 2010). Here we report a surprising new observation: An electronic configuration in the N=1 second LL whose resistivity tensor simultaneously displays a robust fractionally quantized Hall plateau and a strongly anisotropic longitudinal resistance resembling that of the stripe phases.