title: Low energy quasiparticle excitation in the vortex state of borocarbide superconductor yni2b2c.
abstract: We measured the heat capacity C(p) and microwave surface impedance Z(s) in the vortex state of YNi2B2C. In contrast to conventional s-wave superconductors, C(p) shows a square root[H] dependence. This square root[H] dependence persists even after the introduction of the columnar defects which change the electronic structure of the vortex core regime and destroy the regular vortex lattice. On the other hand, flux flow resistivity is nearly proportional to H. These results indicate that the vortex state of YNi2B2C is fundamentally different from the conventional s-wave counterparts, in that the delocalized quasiparticle states around the vortex core are important, similar to d-wave superconductors.
authors.affiliation: Institute of Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Izawa
authors.forename: A
authors.initials: A
authors.lastname: Shibata
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: H
authors.initials: H
authors.lastname: Takeya
authors.forename: K
authors.initials: K
authors.lastname: Hirata
authors.forename: C J
authors.initials: CJ
authors.lastname: van Der Beek
authors.forename: M
authors.initials: M
authors.lastname: Konczykowski