Observation of inter-Landau-level quantum coherence in semiconductor quantum wells

TL;DR

This study demonstrates the existence of long-lived inter-Landau-level quantum coherence in semiconductor quantum wells, revealing new intraband excitation dynamics through femtosecond spectroscopy and many-body theory analysis.

Contribution

It provides the first experimental observation and theoretical interpretation of inter-Landau-level quantum coherence with longer decay times than interband dephasing.

Findings

Observation of quantum beats indicating inter-Landau-level coherence

Decoherence time longer than interband magnetoexciton dephasing

Identification of new intraband excitation dynamics

Abstract

Using three-pulse four-wave-mixing femtosecond spectroscopy, we excite a non-radiative coherence between the discrete Landau levels of an undoped quantum well and study its dynamics. We observe quantum beats that reflect the time evolution of the coherence between the two lowest Landau level magnetoexcitons. We interpret our observations using a many-body theory and find that the inter Landau level coherence decays with a new time constant, substantially longer than the corresponding interband magnetoexciton dephasing times. Our results indicate a new intraband excitation dynamics that cannot be described in terms of uncorrelated interband excitations.