Spin dynamics in semiconductor nanocrystals

TL;DR

This study investigates spin relaxation processes in CdSe nanocrystals using time-resolved Faraday rotation, revealing size-dependent spin dynamics and multiple relaxation timescales influenced by temperature and magnetic field.

Contribution

It provides a detailed analysis of both transverse and longitudinal spin relaxation in semiconductor nanocrystals, including the assignment of spin precession frequencies and the impact of inhomogeneous dephasing.

Findings

Transverse spin lifetime limited by inhomogeneous dephasing beyond size distribution effects

Longitudinal spin relaxation occurs over 100 ps to 10 microseconds with different temperature and field dependencies

Distinct spin precession frequencies assigned to electron and exciton spins based on size and theoretical models

Abstract

Time-resolved Faraday rotation is used to study both transverse and longitudinal spin relaxation in chemically-synthesized CdSe nanocrystals (NCs) 22-80 Angstroms in diameter. The precession of optically-injected spins in a transverse magnetic field occurs at distinct frequencies whose assignment to electron and exciton spins is developed through systematic studies of the size-dependence and theoretical calculations. It is shown that the transverse spin lifetime is limited by inhomogeneous dephasing to a degree that cannot be accounted for by the NC size distribution alone. Longitudinal spin relaxation in these NCs occurs on several distinct timescales ranging from 100 ps-10 microseconds and exhibits markedly different dependencies on temperature and field in comparison to transverse spin relaxation.