Friction on a Quantized Vortex in a Superfluid

We obtain the explicit expression of the friction on a moving quantized vortex, following the formulation of Thouless, Ao and Niu. It is shown that the friction on a moving vortex is sensitive to details but does not change the transverse force. We provide a general thermodynamic interpretation for the mutual independence of the transverse force and the friction. The friction is evaluated for the case of quasiparticle contributions in a clean fermionic superfluid, showing a new feature of logarithmic divergence. PACS#s: 67.40.Vs; 47.37.+8 In physical systems few qualities have generic values independent of material details. When such cases occur, usually there are either symmetry or topology reasons[1]. The controversy over dynamics of quantized vortices in superfluids or superconductors[2, 3] may be partly understood as due to the apparent conflict between the exact results[4, 5, 6] with the existence of various scattering processes in the system. When a vortex moves, in addition to the hydrodynamic Magnus force which is proportional to the superfluid density, the coupling between the vortex to quasiparticles, phonons and impurities may cause extra forces in both transverse and longitudinal directions of the vortex motion. Those possible non-vanishing forces have always been the underlying assumption for phenomenological models used in analyzing experiments[2, 7].