Heavy hole states in Germanium hut wires

TL;DR

This study investigates heavy hole states in Ge hut wires, revealing significant anisotropy in g-factors due to wave function confinement, with implications for spin qubits and long spin lifetimes.

Contribution

It is the first to explore hole spins in Ge hut wires, demonstrating large g-factor anisotropy and confirming heavy hole character through numerical simulations.

Findings

Large anisotropy between in-plane and out-of-plane g-factors (up to 18).

Wave functions are predominantly heavy hole with minimal light hole admixture.

Spin lifetimes are expected to be very long, even without isotopic purification.

Abstract

Hole spins have gained considerable interest in the past few years due to their potential for fast electrically controlled qubits. Here, we study holes confined in Ge hut wires, a so far unexplored type of nanostructure. Low temperature magnetotransport measurements reveal a large anisotropy between the in-plane and out-of-plane g-factors of up to 18. Numerical simulations verify that this large anisotropy originates from a confined wave function which is of heavy hole character. A light hole admixture of less than 1% is estimated for the states of lowest energy, leading to a surprisingly large reduction of the out-of-plane g-factors. However, this tiny light hole contribution does not influence the spin lifetimes, which are expected to be very long, even in non isotopically purified samples.