Split-Channel Ballistic Transport in an InSb Nanowire

TL;DR

This study investigates ballistic 1D electronic transport in an InSb nanowire with gate-tunable conductance, revealing Zeeman splitting, subband degeneracy, and resonant states, explained by two spatially separated conduction channels.

Contribution

It demonstrates gate-controlled formation of two spatially separated 1D channels and observes tunable conductance features, including Zeeman splitting and subband degeneracy, in InSb nanowires.

Findings

Observation of conductance plateaus at multiples of e^2/h

Detection of a two-fold subband degeneracy persisting up to several Tesla

Presence of discrete resonant states resembling helical gap features

Abstract

We report an experimental study of one-dimensional (1D) electronic transport in an InSb semiconducting nanowire. Three bottom gates are used to locally deplete the nanowire creating a ballistic quantum point contact with only a few conducting channels. In a magnetic field, the Zeeman splitting of the corresponding 1D subbands is revealed by the emergence of conductance plateaus at multiples of $e^2$/h, yet we find a quantized conductance pattern largely dependent on the configuration of voltages applied to the bottom gates. In particular, we can make the first plateau disappear leaving a first conductance step of 2$e^2/h$, which is indicative of a remarkable two-fold subband degeneracy that can persist up to several Tesla. For certain gate voltage settings, we also observe the presence of discrete resonant states producing conductance features that can resemble those expected from the opening of a helical gap in the subband structure. We explain our experimental findings through the formation of two spatially separated 1D conduction channels.