Microscopic Quantum Friction

Abstract

We report on a microscopic theory of quantum friction. Our approach investigates the interplay between the dispersive response and the relative center-of-mass motion of two ground-state atoms. This coupling yields a quantum force, which can be expressed as a power series in the velocity. The significance of each contribution depends on its order parity: while even-order terms are reversible, odd-order terms are irreversible and only survive in the presence of an internal dissipation mechanism. In addition, we obtain general, model-independent properties for the work performed by these contributions for arbitrary scattering trajectories. These results enable an unambiguous identification of odd-parity terms with microscopic quantum friction. At room temperature, the dominant microscopic quantum friction is of first order in the velocity and presents a strong quantum character. Our microscopic theory reveals that several properties of quantum friction obtained in specific settings -- such as the cubic dependence on velocity at zero temperature -- are indeed universal features already present at the atomic scale.

Figures (1)

• Figure 1: a) Schematics of atom $B$ moving in uniform motion with respect to atom $A$. b) Plot of $F^{(1)}_x$ and $F^{(3)}_x$ versus the relative lateral position $x$ normalized by the minimum distance $z_0$. The forces are normalized by $f=|F^{(1)}(\boldsymbol{r}=z_0\boldsymbol{\hat{z}})|$ and we chose parameters of temperature, velocity and distance such as $(kTz_0/\hbar v)^2=0.05$. The inset reveals that $F^{(3)}_x$ can be locally positive, corresponding to energy transfer to the CM.