Electrical pump-and-probe study of spin singlet-triplet relaxation in a quantum dot

TL;DR

This study investigates spin relaxation mechanisms in semiconductor quantum dots using electrical pump-and-probe techniques, revealing cotunneling effects at high tunneling rates and spin-orbit interactions at lower rates, with implications for quantum information processing.

Contribution

It provides experimental evidence distinguishing cotunneling and spin-orbit interactions as dominant relaxation pathways in quantum dots, based on tunneling rate dependence.

Findings

Relaxation rate depends on tunneling rate squared, indicating cotunneling dominance.

Suppressed cotunneling reveals intrinsic spin-orbit relaxation behavior.

Observed double-exponential decay suggests a specific spin-orbit interaction selection rule.

Abstract

Spin relaxation from a triplet excited state to a singlet ground state in a semiconductor quantum dot is studied by employing an electrical pump-and-probe method. Spin relaxation occurs via cotunneling when the tunneling rate is relatively large, confirmed by a characteristic square dependence of the relaxation rate on the tunneling rate. When cotunneling is suppressed by reducing the tunneling rate, the intrinsic spin relaxation is dominated by spin-orbit interaction. We discuss a selection rule of the spin-orbit interaction based on the observed double-exponential decay of the triplet state.