Phase transitions in a system of indirect magnetoexcitons in coupled quantum wells at high magnetic field: the role of disorder

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Collective properties of a quasi-two-dimensional (2D) system of spatially indirect magnetoexcitons in coupled quantum wells (CQW) in high magnetic field H were analyzed in the presence of disorder. The Hamiltonian of the dilute gas of magnetoexcitons with dipole-dipole repulsion in a random field has been reduced to the Hamiltonian of a dilute gas of dipolar excitons without an applied magnetic field, but in an H-dependent effective random field and having an effective mass of magnetoexciton which is a function of the magnetic field and parameters of the CQW. For 2D magnetoexcitonic systems, the increase of the magnetic field H and the interwell distance D is found to increase the effective renormalized random field parameter Q and suppress the superfluid density nₛ and the temperature of the Kosterlitz-Thouless transition Tc. It is shown that in the presence of the disorder there is a quantum transition to the superfluid state at zero temperature T=0 with respect to the magnetic field H and the parameters of the disorder. There is no superfluidity at any exciton density in the presence of the disorder at sufficiently large magnetic field H or sufficiently large disorder.