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-type tetragonal crystal structureMaehira, Takahiro*; Hotta, Takashi; Ueda, Kazuo*; Hasegawa, Akira*
New Journal of Physics (Internet), 8(2), p.24_1 - 24_20, 2006/02
Times Cited Count：16 Percentile：64.61(Physics, Multidisciplinary)By using a relativistic band-structrue calculation method, we investigate energy band structures and the Fermi surfaces of NpTGa, PuTGa, and AmCoGa with transition metal atoms T. It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between 
and Ga 
electrons. For PuTGa, we observe several cylindrical sheets of Fermi surfaces with large volume for T=Co, Rh, and Ir. It is also found that the Fermi surfaces of NpFeGa, NpCoGa, and NpNiGa are similar to those of UCoGa, UNiGa, and PuCoGa, respectively, except for small details. For AmCoGa, the Fermi surfaces are found to consist of large cylindrical electron sheets and small closed hole sheets, similar to PuCoGa. The similarity is basically understood by a rigid-band picture.
(T=Fe, Co, Rh)Maehira, Takahiro; Higuchi, Masahiko*; Hasegawa, Akira*
Physica B; Condensed Matter, 329-333(1-4), p.574 - 575, 2003/05
Times Cited Count：20 Percentile：66.95(Physics, Condensed Matter)The relativistic energy-band calculations have been carried out for 
, 
and 
under the assumption that 5
-electrons are itinerant. A hybridization between the U 5 state and Ga 4
state occurs in the vicinity of the Fermi level. The Fermi surface of is quite similar to that of , which are all small in size and closed in topology. has the quasi-two-dimensional Fermi surface which looks like a lattice structure.
(T=Rh, Ir, and Co); Band-calculation and tight-binding approachMaehira, Takahiro; Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*; Higuchi, Masahiko*; Hasegawa, Akira*
Journal of the Physical Society of Japan, Vol.71, Supplement, p.285 - 287, 2002/00
Times Cited Count：8 Percentile：49.89(Physics, Multidisciplinary)Recently a new family of Ce-based heavy fermion superconductor 
(T=Rh, Ir, and Co) has been reported. The dHvA effect has been successfully observed in 
and 
.The angular dependence of dHvA branches is well explained by a quasi-two dimensional Fermi surface(F.S.). In order to clarify band structures of Ce-115 systems such as CeIrIn and CeCoGa, two-step strategy is here employed. In the first step, the F.S. are derived by using the RLAPW method. In the next step, the band structure near the Fermi level is reanalyzed by using a simple tight-binding model. Namely, hopping amplitudes of -electrons between neighboring Ce ions are parameterized to reproduce the F.S. obtained in the band-calculation. By further adding the Coulomb interaction terms into this tight-binding model, a simple many-body Hamiltonian for Ce-compounds can be constructed. This Hamiltonian opens a way to discuss magnetism and superconductivity in -electron systems from the microscopic viewpoint.
