Huge upper critical field in the superconductor with non-centrosymmetric crystal structure CeCoGe

反転中心を持たない結晶構造を持つCeCoGeの超伝導状態における巨大上部臨界磁場

Masson, M.-A.*; 村中 大志*; 松田 達磨; 河井 友也*; 芳賀 芳範   ; Knebel, G.*; 青木 大*; Lapertot, G.*; 本多 史憲*; 摂待 力生*; Brison, J. P.*; Flouquet, J.*; 清水 克哉*; 大貫 惇睦*

Masson, M.-A.*; Muranaka, Hiroshi*; Matsuda, Tatsuma; Kawai, Tomoya*; Haga, Yoshinori; Knebel, G.*; Aoki, Dai*; Lapertot, G.*; Honda, Fuminori*; Settai, Rikio*; Brison, J. P.*; Flouquet, J.*; Shimizu, Katsuya*; Onuki, Yoshichika*

We report the upper critical field, , of the non-centrosymmetric compound CeCoGe by resistivity measurements under high pressure of 7.1 GPa, for along and axis, and for a magnetic field up to 17T. is very anisotropic, saturating at low temperature for along the axis and linear for along the axis. Very high () is observed for along the axis, with a huge value of the slope d/d =-47 1.3 T/K, the highest ever reported if normalized to the superconducting temperature of 0.65 K. This is most probably related to a conjunction of a heavy fermionic state and the absence of the Pauli limitation. A fit of () shows that the curves for a and axis can be reproduced with a moderate coupling Eliashberg theory.