Phase-Sensitive Flux-Flow resistivity in Unconventional Superconductors

We theoretically investigate the magnetic-field-angle dependence of the flux-flow resistivity $\rho_{\rm f}$ in unconventional superconductors. Two contributions to $\rho_{\rm f}$ are considered: one is the quasiparticle (QP) relaxation time $\tau(\bm{k}_{\rm F})$ and the other is $\omega_0(\bm{k}_{\rm F})$, which is a counterpart to the interlevel spacing of the QP bound states in the quasiclassical approach. Here, $\bm{k}_{\rm F}$ denotes the position on a Fermi surface. Numerical calculations are conducted for a line-node s-wave and a d-wave pair potential with the same anisotropy of their amplitudes, but with a sign change only for a d-wave one. We show that the field-angle dependence of $\rho_{\rm f}$ differs prominently between s-wave and d-wave pairs, reflecting the phase of the pair potentials. We also discuss the case where $\tau$ is constant and compare it with the more general case where $\tau$ depends on $\bm{k}_{\rm F}$.