Magneto-optical readout of dark exciton distribution in cuprous oxide

TL;DR

This study demonstrates a magneto-optical method to analyze the distribution and dynamics of dark paraexcitons in Cu2O, providing insights relevant for Bose-Einstein condensation research.

Contribution

It introduces a novel optical activation technique for dark paraexcitons in strong magnetic fields, enabling direct observation of their distribution and evolution.

Findings

Optical activation of paraexcitons via magnetic mixing.

Time-resolved data on paraexciton thermodynamics.

Potential for Bose-Einstein condensation studies.

Abstract

An experimental study of the yellow exciton series in Cu2O in strong magnetic fields up to 32 T shows the optical activation of direct and phonon-assisted paraexciton luminescence due to mixing with the quadruple allowed orthoexciton state. The observed phonon-assisted luminescence yields information on the statistical distribution of occupied states. Additional time-resolved experiments provide a unique opportunity to directly determine the time evolution of the thermodynamical properties of the paraexciton gas. Because the lifetime of paraexciton is hardly affected by the optical activation in a strong magnetic field, this opens new possibilities for studies aiming at Bose-Einstein condensation of excitons in bulk semiconductors.