Unusual conductance collapse in one-dimensional quantum structures

TL;DR

This paper reports an unusual insulating state in one-dimensional quantum wires where conductance abruptly drops to zero, likely due to many-body effects like charge density waves or Wigner crystallization, with distinct collapse behaviors observed under different conditions.

Contribution

It reveals two types of conductance collapse in quantum wires with non-uniform confinement, highlighting their thermal activation and voltage thresholds, and discusses their relation to many-body phenomena.

Findings

Conductance drops by over three orders of magnitude in certain wire configurations.

The collapse is thermally activated with an energy around 1 K.

A voltage threshold induces a steep conductance rise, indicating a density of states gap.

Abstract

We report an unusual insulating state in one-dimensional quantum wires with a non-uniform confinement potential. The wires consist of a series of closely spaced split gates in high mobility GaAs/AlGaAs heterostructures. At certain combinations of wire widths, the conductance abruptly drops over three orders of magnitude, to zero on a linear scale. Two types of collapse are observed, one occurring in multi-subband wires in zero magnetic field and one in single subband wires in an in-plane field. The conductance of the wire in the collapse region is thermally activated with an energy of the order of 1 K. At low temperatures, the conductance shows a steep rise beyond a threshold DC source-drain voltage of order 1 mV, indicative of a gap in the density of states. Magnetic depopulation measurements show a decrease in the carrier density with lowering temperature. We discuss these results in the context of many-body effects such as charge density waves and Wigner crystallization in quantum wires.