Anomalous quasiparticle transport in the superconducting state ofCeCoIn5

Abstract

We report on a study of thermal Hall conductivity ${\ensuremath{\kappa}}_{xy}$ in the superconducting state of ${\mathrm{CeCoIn}}_{5}$. The scaling relation and the density of states of the delocalized quasiparticles, both obtained from ${\ensuremath{\kappa}}_{xy}$, are consistent with $d$-wave superconducting symmetry. The onset of superconductivity is accompanied by a steep increase in the thermal Hall angle, pointing to a striking enhancement in the quasiparticle mean free path. This enhancement is drastically suppressed in a very weak magnetic field. These results highlight that ${\mathrm{CeCoIn}}_{5}$ is unique among superconductors. A small Fermi energy, a large superconducting gap, a short coherence length, and a long mean free path all indicate that ${\mathrm{CeCoIn}}_{5}$ is clearly in the superclean regime $({\ensuremath{\epsilon}}_{F}∕\ensuremath{\Delta}⪡\ensuremath{\ell}∕\ensuremath{\xi})$, in which a peculiar vortex state is expected.