Conference on Lasers and Electro-Optics

Spontaneous coherence, interaction and kinetics of macroscopically ordered exciton state

Sen Yang, Aeron Tynes Hammack, A. V. Mintsev, M. M. Fogler, Леонид Викторович Бутов, Leonid S Levitov, Benjamin D. Simons, Arthur C. Gossard

Published May 4, 2008• 0 citations

Publisher

Abstract

The macroscopically ordered exciton state (MOES) appears in the external exciton rings in GaAs/(Al,Ga)As coupled quantum wells below a few Kelvin. Here, we report on the experimental study of coherence, interaction and kinetics of MOES.

DOI: 10.1109/qels.2008.4553133

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Conference on Lasers and Electro-Optics

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We present an experimental and theoretical investigation of ultrafast transient four-wave mixing of GaAs/

{\mathrm{Al}}_{\mathit{x}}

${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum wells for coherent excitation of exciton and continuum states. The signal appears at the exciton resonance and is shown to consist of two contributions: an intense spectrally narrow part only present for short time delays and a weak exponentially decaying part reflecting the intrinsic coherence properties of the exciton states. The intense part of the signal is due to the excitation of the continuum states mediated by interaction-induced nonlinearities. \textcopyright{} 1996 The American Physical Society.

{J}_{\mathrm{ex}},

we study the stationary spatial pattern of the phase of the condensate wave function. It is shown that there appears a vortex lattice with a net supercurrent when

{J}_{\mathrm{ex}}

is larger than a critical value; the period of the lattice is determined as a function of

{J}_{\mathrm{ex}}.

We calculate the magnetic field induced by the current in the vortex lattice, and discuss a possibility of an experimental observation of the critical current. Such a direct observation of the exciton transport will provide unambiguous experimental evidence for the superfluidity of excitons.