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arXiv · 2009.10596

Stochastic motion of finite-size immiscible impurities in a dilute quantum fluid at finite temperature

Umberto Giuriato·Giorgio Krstulovic
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Abstract

The dynamics of an active, finite-size and immiscible impurity in a dilute quantum fluid at finite temperature is characterized by means of numerical simulations of the projected Gross--Pitaevskii equation. The impurity is modeled as a localized repulsive potential and described with classical degrees of freedom. It is shown that impurities of different sizes thermalize with the fluid and undergo a stochastic dynamics compatible with an Ornstein--Uhlenbeck process at sufficiently large time-lags. The velocity correlation function and the displacement of the impurity are measured and an increment of the friction with temperature is observed. Such behavior is phenomenologically explained in a scenario where the impurity exchanges momentum with a dilute gas of thermal excitations, experiencing an Epstein drag.

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Umberto Giuriato, Giorgio Krstulovic. 2020-12-16. Stochastic motion of finite-size immiscible impurities in a dilute quantum fluid at finite temperature. https://doi.org/10.1103/physrevb.103.024509

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