Jueves 17 de mayo 2012

15h00-16h30 “Non-conventional superconductivity and Anisotropic Spin Fluctuation in Heavy-Fermion Systems”

Prof: Sinsaku KAMBE (Adanced Science Research Center, Japan Atomic Energy Agency; SPSMS/INAC CEA Grenoble).


In unconventional superconductors, suprconducting. Cooper pairs are believed to be formed via magnetic fluctuations. In Fact, the superconducting transition temperature Tc roughly correales with the antiferromagnetic spin fluctuation energy in d-wave unconventional superconductors including high Tc-cuprates. In addition to this correlation, the suprconducting pairing symmetry and the magnetic anisotropy of the normal satate are found empirically to be strongly correlated in f-electron unconventional superconductors. Unconventional superconductivity appears with singlet (d-wave) pairing for cases of XY anisotropy, incontrast, in ferromagnetic systems, unconventional superconductivity with triplet (e.g. p-wave) pairing appears for cases of Ising anisotropy.  Furthermore Tc  is found to correlate with the strength of XY anisotropy determined by NMR in d-wave cases. In this presentation, the origin of XY anisotropy is discussed in terms of the orbital character, i.e. the angular momentum character jz  of j=5/2 multiplet for each piece of Fermi surfaces. Exceptional cases e.g. URu2Si2 from this correlation between magnetic anisotropy and unconventional superconductivity seem to have an interesting reason for the exception, wich wil be also addressed.