title: Electronic structure of pyrochlore Cd(2)Re(2)O(7).
abstract: Detailed band structure calculations have been performed for Cd(2)Re(2)O(7) in high-, middle- and low-temperature (T) phases. The calculations are based on the observed lattice structures from x-ray diffraction measurements. The spin-orbit interaction is incorporated self-consistently in both the generalized gradient approximation (GGA) and the GGA plus Hubbard U (GGA+U) approaches. It is found that the on-site U has negligible effects on the Re 5d band structures; therefore both the GGA and GGA+U Re 5d band energies agree well with the observed O K-edge x-ray absorption spectroscopy (XAS) spectrum, whereas the Cd 4d band energy observed from photoemission spectroscopy can only be correctly reproduced by GGA+U calculations, indicating the relatively itinerant Re 5d and localized Cd 4d electrons. On the other hand, the spin-orbit coupling gives rise to nontrivial spin and orbital magnetic moments for the middle- T phase. Most unexpectedly, we found that the low- T phase exhibits quasi-two-dimensional Fermi surfaces. The calculated carrier numbers for the three phases are, at least qualitatively, consistent with the measured Hall coefficient.
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan. Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan.
authors.forename: Shih-Wen
authors.initials: SW
authors.lastname: Huang
authors.forename: Horng-Tay
authors.initials: HT
authors.lastname: Jeng
authors.forename: J-Y
authors.initials: JY
authors.lastname: Lin
authors.forename: W J
authors.initials: WJ
authors.lastname: Chang
authors.forename: J M
authors.initials: JM
authors.lastname: Chen
authors.forename: G H
authors.initials: GH
authors.lastname: Lee
authors.forename: H
authors.initials: H
authors.lastname: Berger
authors.forename: H D
authors.initials: HD
authors.lastname: Yang
authors.forename: Keng S
authors.initials: KS
authors.lastname: Liang