Giant Superfluorescent Bursts from a Semiconductor Magnetoplasma

TL;DR

This paper reports the observation of giant superfluorescent bursts in a semiconductor magnetoplasma, demonstrating macroscopic coherence and cooperative emission in an ultradense electron-hole plasma with picosecond pulses.

Contribution

It provides the first experimental demonstration of superfluorescence in a semiconductor system, expanding the understanding of cooperative quantum phenomena beyond atomic and molecular contexts.

Findings

Observation of intense, delayed superfluorescent pulses with picosecond duration.

Superfluorescent bursts occur only at high excitation powers, magnetic fields, and low temperatures.

Theoretical simulations successfully explain the experimental features.

Abstract

Currently, considerable resurgent interest exists in the concept of superradiance (SR), i.e., accelerated relaxation of excited dipoles due to cooperative spontaneous emission, first proposed by Dicke in 1954. Recent authors have discussed SR in diverse contexts, including cavity quantum electrodynamics, quantum phase transitions, and plasmonics. At the heart of these various experiments lies the coherent coupling of constituent particles to each other via their radiation field that cooperatively governs the dynamics of the whole system. In the most exciting form of SR, called superfluorescence (SF), macroscopic coherence spontaneously builds up out of an initially incoherent ensemble of excited dipoles and then decays abruptly. Here, we demonstrate the emergence of this photon-mediated, cooperative, many-body state in a very unlikely system: an ultradense electron-hole plasma in a semiconductor. We observe intense, delayed pulses, or bursts, of coherent radiation from highly photo-excited semiconductor quantum wells with a concomitant sudden decrease in population from total inversion to zero. Unlike previously reported SF in atomic and molecular systems that occur on nanosecond time scales, these intense SF bursts have picosecond pulse-widths and are delayed in time by tens of picoseconds with respect to the excitation pulse. They appear only at sufficiently high excitation powers and magnetic fields and sufficiently low temperatures - where various interactions causing decoherence are suppressed. We present theoretical simulations based on the relaxation and recombination dynamics of ultrahigh-density electron-hole pairs in a quantizing magnetic field, which successfully capture the salient features of the experimental observations.