Spin fluctuation, orbital states and non-conventional superconductivity in actinides compounds

アクチノイド化合物のスピン揺らぎ,軌道状態と新奇超伝導

神戸 振作  ; 酒井 宏典   ; 徳永 陽  

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo

波超伝導体では、超伝導クーパー対は磁気揺らぎによって誘起されている。実際、反強磁性磁気揺らぎエネルギーと超伝導転移温度は、高温超伝導体を含む波超伝導体で相関がある。この相関に加え、電子系の新奇超伝導体では、磁気異方性と超伝導対称性に相関が見られる。反強磁性新奇超伝導にはXY型揺らぎが有利であり、強磁性新奇超伝導にはISING揺らぎが有利である。ここではXY型磁気異方性の起源について軌道角運動量とFermi面の観点から議論する。

In -wave unconventional superconductors, superconducting Cooper pairs are believed to be formed via magnetic fluctuations. In fact, superconducting transition temperature roughly correlates with antiferromagnetic spin fluctuation energy in -wave unconventional superconductors including high cuprates. In addition to this correlation, the superconducting pairing symmetry and the magnetic anisotropy of the normal state are found empirically to be strongly correlated in -electron unconventional superconductors having crystallographic symmetry lower than cubic. In antiferromagnetic systems, unconventional superconductivity appears with singlet (-wave) pairing for cases of XY anisotropy. In contrast, in ferromagnetic systems, unconventional superconductivity with triplet (e.g. -wave) pairing appears for cases of Ising anisotropy. In this report, the origin of XY anisotropy is discussed in terms of the angler momentum character for each Fermi surfaces.