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Abstract: We investigate the thermodynamic properties of a dilute Bose gas in acorrelated random potential using exact path integral Monte Carlo methods. Thestudy is carried out in continuous space and disorder is produced in thesimulations by a 3D speckle pattern with tunable intensity and correlationlength. We calculate the shift of the superfluid transition temperature due todisorder and we highlight the role of quantum localization by comparing thecritical chemical potential with the classical percolation threshold. Theequation of state of the gas is determined in the regime of strong disorder,where superfluidity is suppressed and the normal phase exists down to very lowtemperatures. We find a $T^2$ dependence of the energy in agreement with theexpected behavior in the Bose glass phase. We also discuss the major roleplayed by the disorder correlation length and we make contact with aHartree-Fock mean-field approach that holds valid if the correlation length isvery large. The density profiles are analyzed as a function of temperature andinteraction strength. Effects of localization and the depletion of the orderparameter are emphasized in the comparison between local condensate and totaldensity. At very low temperature we find that the energy and the particledistribution of the gas are very well described by the T=0 Gross-Pitaevskiitheory even in the regime of very strong disorder.



Author: S. Pilati, S. Giorgini, M. Modugno, N. Prokof'ev

Source: https://arxiv.org/







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