title: Ubiquitous V-shape density of states in a mixed state of clean limit type II superconductors.
abstract: It is demonstrated theoretically and experimentally that the low energy density of states N(E) is described by a singular V-shape form N(E)=N(0)(H)+alpha|E|+O(E2) for all clean superconductors in a vortex state, irrespective of the underlying gap structure. The linear term alpha|E| which has not been recognized so far is obtained by exactly evaluating the vortex contribution. Based on microscopic Eilenberger theory N(E) is evaluated for the isotropic gap, line, and point-node gaps to yield a V-shape N(E). Scanning tunneling spectroscopy-STM experiments on NbSe2 and YNi2B2C give direct evidence for this. We provide arguments on the significance of this finding and on the relevance to other experiments.
authors.affiliation: Department of Physics, Okayama University, Okayama 700-8530, Japan. nakai@mp.okayama-u.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Nakai
authors.forename: P
authors.initials: P
authors.lastname: Miranović
authors.forename: M
authors.initials: M
authors.lastname: Ichioka
authors.forename: H F
authors.initials: HF
authors.lastname: Hess
authors.forename: K
authors.initials: K
authors.lastname: Uchiyama
authors.forename: H
authors.initials: H
authors.lastname: Nishimori
authors.forename: S
authors.initials: S
authors.lastname: Kaneko
authors.forename: N
authors.initials: N
authors.lastname: Nishida
authors.forename: K
authors.initials: K
authors.lastname: Machida