Electronic Structure, Photoemission and Superconductivity in PuCoGa 5
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1264-Z12-03
Electronic Structure, Photoemission and Superconductivity in PuCoGa5 A. B. Shick1, S. Khmelevskyi2, and L. Havela3. 1
Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221
Prague, Czech Republic. 2
CMS, Institute of Applied Physics, Vienna Univ. of Technology, Makkartvilla, Gusshausstrasse
25a, A-1030 Vienna, Austria. 3
Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 12116
Prague, Czech Republic. ABSTRACT We study theoretically the electronic structure and photoemission spectra of PuCoGa5 making use of the LDA+Hubbard I approximation implemented in the full-potential LAPW basis, including self-consistency over the charge density. The calculations show relative reduction of the f-states spectral weight at the Fermi energy. There is fairly good agreement between calculated photoemission spectra and experimental results. We demonstrate that an account of Pu f-electron Coulomb correlations does not modify significantly the Fermi surface topologies but leads to substantial reduction of the f-character for the electronic states at the Fermi energy. These findings can be important for the theory of superconductivity in PuCoGa5 and related compounds. INTRODUCTION Discovery of superconductivity in PuCoGa5 [1] led to detailed experimental and theoretical studies of the electronic, magnetic, spectroscopic and superconducting properties of a few groups of the f-electron materials believed to be connected to PuCoGa5. The nature of the mediating bosons in the superconductive phase of PuCoGa5 is still a controversy. The most commonly accepted viewpoint is that this material is an unconventional superconductor mediated by spin fluctuations [2]. Nevertheless, the polarized neutron scattering experiments [3] have shown that the normal state of PuCoGa5 is different from that anticipated for a Pu-f 5 ion, since the magnetic susceptibility in the normal state is weak, temperature independent and dominated by orbital effects. The modern electronic structure theory has been applied to study the normal phase of PuCoGa5 and related compounds. The conventional local density approximation (LDA) applied to PuCoGa5 [4] suggested that the superconductivity dominantly emerges due to the 5f-states of Pu. The LDA densities of states (DOS) were later used by Ummarino et al [5] in an attempt to develop phonon-mediated strong-coupling theory of superconductivity in PuCoGa5. Solving numerically the Eliashberg equations for two-band model and assuming the d-wave superconducting gap symmetry, Ummarino et al. [5] obtained temperature dependence of the superconducting gap and quasi-particle DOS. It was shown that the use of electron-phonon coupling allows reproducing experimental normal phase resistivity temperature dependence up to
the room temperature. While LDA results [4] are often used as an input for superconductivity theories [5], their validity is not at all justified for strongly correlated f-electron solids. In this work we study the electron correlation effects in the
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