Condensed Matter Seminars

Vortices in clean d-wave superconductors at low temperatures can behave as quantum particles. Their quantum dynamics is made possible by the smallness of their cores, due to short coherence length in typical cuprates, and by the presence of massless fermionic quasiparticles, which give rise to certain universal effects. We calculate a small finite renormalization of vortex mass by the nodal quasiparticles, and demonstrate the absence of Bardeen-Stephen damping of vortex motion in the limits of zero temperature, no disorder and vanishing core size. Being liberated from strong friction, light vortices can experience significant quantum fluctuations that can explain several phenomena observed in cuprates, including the Nernst effect and density waves. We also show that quantum fluctuations of localized vortices can significantly affect quasiparticle spectra. The local electronic density of states (LDOS) near a quantum fluctuating vortex shows no zero-energy peak, but has satellite features at energies set by the vortex trapping potential. These are proposed to be the origin of the sub-gap LDOS peaks observed in recent STM experiments near the vortex cores.