Fast exciton spin relaxation in single quantum dots

TL;DR

This study reveals that exciton spin relaxation in single quantum dots occurs much faster than previously thought, with relaxation times under 100 ps, challenging the idea of frozen exciton spins in such systems.

Contribution

The paper provides experimental evidence that exciton spin relaxation in single quantum dots is rapid, contradicting the expectation of spin quenching and offering new insights into spin dynamics.

Findings

Exciton spin relaxation time is ≤100 ps at low temperature.

Polarization anisotropy measurements show rapid spin relaxation.

Results challenge the concept of frozen exciton spins in quantum dots.

Abstract

Exciton spin relaxation is investigated in single epitaxially grown semiconductor quantum dots in order to test the expected spin relaxation quenching in this system. We study the polarization anisotropy of the photoluminescence signal emitted by isolated quantum dots under steady-state or pulsed non-resonant excitation. We find that the longitudinal exciton spin relaxation time is strikingly short ($\leq$100 ps) even at low temperature. This result breaks down the picture of a frozen exciton spin in quantum dots.