Phase-Sensitive Measurements of Vortex Dynamics in the Terahertz Domain

Phase-sensitive spectroscopy is used to characterize fully the complex resistivity tensor of YB${\mathrm{a}}_2$C${\mathrm{u}}_3$ ${\mathrm{O}}_x$ films in the mixed state, in the frequency range 100 to 500 GHz and temperature range 10 K to $T_c$. We compare our results with the predictions of a vortex model containing three parameters: viscosity, pinning, and Magnus force. The viscosity and Magnus parameter we measure are in disagreement with theoretically predicted values. We show that the discrepancies can be explained by incorporating the effects of a highly anisotropic or $d$-wave gap.