Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2
Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2
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DOI：
10.1103/physrevb.94.054514
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发表时间：
2016-08
影响因子：
3.7
通讯作者：
S. Kittaka;Y. Aoki;Y. Shimura;T. Sakakibara;S. Seiro;C. Geibel;F. Steglich;Y. Tsutsumi;H. Ikeda;K. Machida
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文献类型：
--
作者：
S. Kittaka;Y. Aoki;Y. Shimura;T. Sakakibara;S. Seiro;C. Geibel;F. Steglich;Y. Tsutsumi;H. Ikeda;K. Machida
本文介绍了第一个发现的重费米子超导体CeCu 2Si 2（T_{\rmc} \sim 0.6$ K）的比热和磁化强度的测量结果，特别是它们与磁场方向的关系.我们讨论了超导能隙结构和反常对断裂现象的起源，例如，的抑制的上临界场$H_{\rmc 2}$，发现在高场区。数据表明，在任何磁场方向上，在低于0.15 K时，反常对的破缺都变得显著，但对于H平行c，在更接近H_{\rmc 2}$处出现。比热和磁化强度数据满足标准热力学关系的事实证实了这种异常的存在。关于差距结构，在$ab$和$ac$平面内的低温比热的场角依赖性没有显示出间隙节点的任何证据。在两带全隙模型的框架下，通过微观计算，合理地再现了C$和1/T_1$的幂律温度依赖关系，使人联想到节结超导。这些事实进一步支持了CeCu $_2Si $_2 $的多带全禁带超导性。
This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconductor CeCu$_2$Si$_2$ ($T_{\rm c} \sim 0.6$ K). We discuss the superconducting gap structure and the origin of the anomalous pair-breaking phenomena, leading e.g., to the suppression of the upper critical field $H_{\rm c2}$, found in the high-field region. The data show that the anomalous pair breaking becomes prominent below about 0.15 K in any field direction, but occurs closer to $H_{\rm c2}$ for $H \parallel c$. The presence of this anomaly is confirmed by the fact that the specific-heat and magnetization data satisfy standard thermodynamic relations. Concerning the gap structure, field-angle dependences of the low-temperature specific heat within the $ab$ and $ac$ planes do not show any evidence for gap nodes. From microscopic calculations in the framework of a two-band full-gap model, the power-law-like temperature dependences of $C$ and $1/T_1$, reminiscent of nodal superconductivity, have been reproduced reasonably. These facts further support multiband full-gap superconductivity in CeCu$_2$Si$_2$.