Flux periodic oscillations and phase-coherent transport in GeTe nanowire-based devices

TL;DR

This study reveals phase-coherent transport phenomena in GeTe nanowires, including conductance fluctuations, Aharonov-Bohm oscillations, and Josephson effects, highlighting the material's potential for quantum device applications.

Contribution

First observation of phase-coherent transport and flux-periodic oscillations in GeTe nanowires, demonstrating tubular hole channels and proximity-induced superconductivity.

Findings

Phase-coherence length of ~200nm at 0.5K

Observation of Aharonov-Bohm oscillations

Proximity-induced Josephson current of 0.2μA at 0.4K

Abstract

Despite the fact that GeTe is known to be a very interesting material for applications in thermoelectrics and for phase-change memories, the knowledge on its low-temperature transport properties is only limited. Here, we report on phase-coherent phenomena in the magnetotransport of GeTe nanowires. From universal conductance fluctuations, a phase-coherence length of about 200nm at 0.5K is determined for the hole carriers. The distinct phase-coherence is confirmed by the observation of Aharonov--Bohm type oscillations for magnetic fields applied along the nanowire axis. We interpret the occurrence of these magnetic flux-periodic oscillations by the formation of a tubular hole accumulation layer on the nanowire surface. In addition, for Nb/GeTe-nanowire/Nb Josephson junctions, we obtained a proximity-induced critical current of about 0.2$\mu$A at 0.4K. By applying a magnetic field perpendicular to the nanowire axis, the critical current decreases monotonously with increasing magnetic field, which indicates that the structure is in the small-junction-limit. Whereas, by applying a parallel magnetic field the critical current oscillates with a period of the magnetic flux quantum indicating once again the presence of a tubular hole channel.