Ballistic one-dimensional holes with strong g-factor anisotropy in germanium

TL;DR

This paper demonstrates ballistic hole transport in one-dimensional Ge quantum wires, revealing significant g-factor anisotropy and quantized conductance, advancing potential quantum spintronics applications.

Contribution

It provides experimental evidence of ballistic hole transport with strong g-factor anisotropy in Ge quantum wires, a novel observation for quantum spintronics.

Findings

Quantized conductance observed up to 600 nm channels

G-factor anisotropy with values below 1 in-plane and above 10 out-of-plane

Confirmation of heavy-hole character in valence-band states

Abstract

We report experimental evidence of ballistic hole transport in one-dimensional quantum wires gate-defined in a strained SiGe/Ge/SiGe quantum well. At zero magnetic field, we observe conductance plateaus at integer multiples of 2e^2/h. At finite magnetic field, the splitting of these plateaus by Zeeman effect reveals largely anisotropic g-factors, with absolute values below 1 in the quantum-well plane, and exceeding 10 out of plane. This g-factor anisotropy is consistent with a heavy-hole character of the propagating valence-band states, in line with a predominant confinement in the growth direction. Remarkably, we observe quantized ballistic conductance in device channels up to 600 nm long. These findings mark an important step towards the realization of novel devices for applications in quantum spintronics.