Tagged particle dynamics in supercooled quantum liquids.

Abstract

We analyze the dynamics of quantum supercooled liquids in terms of tagged particle dynamics. Unlike the classical case, uncertainty in the position of a particle in quantum liquid leads to qualitative changes. We demonstrate these effects in the dynamics of the first two moments of displacements, namely, the mean-squared displacement, 〈Δr^{2}(t)〉, and 〈Δr^{4}(t)〉. Results are presented for a hard-sphere liquid using mode-coupling theory formulation and simulation on a binary Lennard-Jones liquid. As the quantumness (controlled by the de Broglie thermal wavelength) is increased, a nonzero value of the moments at zero time leads to significant deviations from the classical behavior in the initial dynamics. Initial displacement shows ballistic behavior 〈Δr^{2}(t)〉∼t^{2}, but, as a result of large uncertainty in the position, the dynamical effects become weaker with increasing quantumness over this timescale.