Nonlinear optical spectroscopy of indirect excitons in biased coupled quantum wells

TL;DR

This study uses time-resolved pump-probe spectroscopy to investigate the spin and population dynamics of indirect excitons in biased coupled quantum wells, revealing their significantly longer spin relaxation times compared to direct excitons and free electrons.

Contribution

It demonstrates the ability to address spin dynamics of indirect excitons despite their low oscillator strength, providing new insights into their relaxation properties.

Findings

Spin relaxation time of indirect excitons exceeds that of direct excitons by two orders of magnitude.

Indirect excitons have longer spin relaxation times than free electrons.

Time-resolved spectroscopy can effectively study spin dynamics of low-oscillator-strength quasi-particles.

Abstract

Indirect excitons in coupled quantum wells are long-living quasi-particles, explored in the studies of collective quantum states. We demonstrate, that despite the extremely low oscillator strength, their spin and population dynamics can by addressed by time-resolved pump-probe spectroscopy. Our experiments make it possible to unravel and compare spin dynamics of direct excitons, indirect excitons and residual free electrons in coupled quantum wells. Measured spin relaxation time of indirect excitons exceeds not only one of direct excitons, but also one of free electrons by two orders of magnitude.