|Budget Amount *help
¥16,700,000 (Direct Cost : ¥16,700,000)
Fiscal Year 2004 : ¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 2003 : ¥13,100,000 (Direct Cost : ¥13,100,000)
Superconductivity with unconventional pairing symmetry has been a central subject in the physics of superconductors. The vast majority of superconductors have conventional s-wave symmetry with an isotropic gap which is independent of directions over the entire Fermi surface. In the last two decades unconventional superconductivity with different symmetry has been found heavy fermion materials, high-Tc cuprates, and organic compounds. Since the nodal structure is ultimately related to the pairing interaction, its identification is crucial for understanding the pairing mechanism.
Recently, thermal conductivity measurements in magnetic field inrotating various directions relative to the crystal axis provide an important information of the superconducting gap structure, inclusing the nodal directions. In this project, we have determined the superconducting gap structure in PrOs4Sb14, UPd2Al3, and CePt3Si, PrOs4Os14 is a recently discovered heavy fermion superconductor with filled skutterdite structure. We found that there are two different superconducting phases with two and four fold symmetry in the superconducting phase, We also showed that UPd2Al3, in which antiferomagnetic order coexists with superconductivity, has horizontal line nodes parallel to the basal plane. In CePt3Si, with no spatial inversion symmetry, we found line nodes.
We also performed ultrasound and NMR measurements on the unconventional superconductor CeCoIn5, wherein we find a novel flux line lattice phase in the vicinity of the upper critical field at very low temperatures. We provide the first compelling evidence of a textured order parameter phase in superconductors, which was predicted some 4 decades ago but never reported experimentally up to now, in spite of extensive exploration in various superconductors.