Two critical pressure in heavy fermion superconductor CePtSi

重い電子系超伝導物質CePtSiにおける2つの臨界圧力

立岩 尚之   ; 芳賀 芳範   ; 松田 達磨; 池田 修悟; 安田 敬*; 竹内 徹也*; 摂待 力生*; 大貫 惇睦

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

昨年、バウアーほかは、結晶構造に反転対称性のないCePtSiで超伝導(=0.75K)と反強磁性(=2.2K)の共存が報告された。われわれは高圧比熱測定を通して、反強磁性・超伝導転移温度の圧力依存性を調べた。反強磁性転移温度は加圧とともに減少し、臨界 0.6GPa前後で消滅する。一方、超伝導状態は1.5GPaまでの幅広い圧力領域に存在する。CePtSiの圧力相図は非常にユニークであり、ほかの重い電子系超伝導物質のそれと異なる特徴を持つ。

Last year, Bauer et al. reported the co-existence of the superconductivity ( = 0.75 K) and antiferromagnetism (= 2.2 K) in CePtSi which has no inversion center in the crystal structure. We have investigated the pressure dependence of the antiferromagnetic and superconducting transition temperatures by ac heat capacity measurement. The Neel temperature decreases with increasing pressure and becomes zero at the critical pressure 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa, which is far above . The pressure phase diagram of CePtSi is thus very unique and has never been reported before for other heavy fermion superconductors.