Broken symmetry states and divergent resistance in suspended bilayer graphene

TL;DR

This study reports on high-quality suspended bilayer graphene devices exhibiting broken symmetry states and divergent resistance, highlighting the role of many-body interactions in these quantum phenomena.

Contribution

The paper demonstrates the fabrication of low-disorder suspended bilayer graphene devices and characterizes their quantum Hall and broken symmetry states at low magnetic fields.

Findings

Observation of fully developed quantized Hall states at 0.2 T

High resistance in the ν=0 state increases with magnetic field

Resistance scales with magnetic field divided by temperature

Abstract

Graphene [1] and its bilayer have generated tremendous excitement in the physics community due to their unique electronic properties [2]. The intrinsic physics of these materials, however, is partially masked by disorder, which can arise from various sources such as ripples [3] or charged impurities [4]. Recent improvements in quality have been achieved by suspending graphene flakes [5,6], yielding samples with very high mobilities and little charge inhomogeneity. Here we report the fabrication of suspended bilayer graphene devices with very little disorder. We observe fully developed quantized Hall states at magnetic fields of 0.2 T, as well as broken symmetry states at intermediate filling factors $\nu = 0$, $\pm 1$, $\pm 2$ and $\pm 3$. The devices exhibit extremely high resistance in the $\nu = 0$ state that grows with magnetic field and scales as magnetic field divided by temperature. This resistance is predominantly affected by the perpendicular component of the applied field, indicating that the broken symmetry states arise from many-body interactions.