Spin-orbit enabled quantum transport channels in a two-hole double quantum dot

TL;DR

This study combines experimental and theoretical approaches to investigate spin-orbit effects in a two-hole double quantum dot, revealing detailed transport spectra, singlet-triplet transitions, and quantum interference phenomena.

Contribution

It provides a comprehensive analysis of spin-orbit enabled transport in a two-hole quantum dot, including experimental measurements and a Hubbard model fit to extract key parameters.

Findings

Identification of the singlet-triplet gap and transition magnetic field.

Observation of resonant current enhancement at the singlet-triplet transition.

Detection of current suppression due to quantum interference effects.

Abstract

We analyze experimentally and theoretically the transport spectra of a gated lateral GaAs double quantum dot containing two holes. The strong spin-orbit interaction present in the hole subband lifts the Pauli spin blockade and allows to map out the complete spectra of the two-hole system. By performing measurements in both source-drain voltage directions, at different detunings and magnetic fields, we carry out quantitative fitting to a Hubbard two-site model accounting for the tunnel coupling to the leads and the spin-flip relaxation process. We extract the singlet-triplet gap and the magnetic field corresponding to the singlet-triplet transition in the double-hole ground state. Additionally, at the singlet-triplet transition we find a resonant enhancement (in the blockaded direction) and suppression of current (in the conduction direction). The current enhancement stems from the multiple resonance of two-hole levels, opening several conduction channels at once. The current suppression arises from the quantum interference of spin-conserving and spin flipping tunneling processes.