Anomalous field-angle dependence of the specific heat of heavy-fermion superconductor UPt

重い電子系超伝導体における比熱の異常な磁場依存性

橘高 俊一郎*; 安 幸治*; 榊原 俊郎*; 芳賀 芳範   ; 山本 悦嗣  ; 木村 憲彰*; 大貫 惇睦; 町田 一成*

Kittaka, Shunichiro*; An, Koji*; Sakakibara, Toshiro*; Haga, Yoshinori; Yamamoto, Etsuji; Kimura, Noriaki*; Onuki, Yoshichika; Machida, Kazushige*

The field-angle variation of the specific heat of the heavy-fermion superconductor UPt at low temperatures down to 50 mK was investigated. The data show that the unusual upper critical field becomes marked only when the magnetic field is pointed close to the -axis. However, the attempt to observe the superconducting gap structure through field-angle dependence of the specific heat failed, because of the small anisotropy compared to the experimental accuracy of 0.5%. It implies that the field-induced excitation of the heavy quasiparticles occur isotropically with respect to the angle.