Heavy-fermion superconductivity: An X-boson treatment

Article

关键词: PERIODIC ANDERSON MODEL;    NARROW ENERGY-BANDS;    CUMULANT EXPANSION;    MIXED-VALENCE;    ELECTRON CORRELATIONS;    SYMMETRY;    SYSTEMS;    LATTICE;    APPROXIMATION;    MOMENT;   

DOI  :  10.1103/PhysRevB.68.134511

来源: SCIE

【 摘 要 】

We use the X-boson method to study the heavy-fermion superconductivity phase, employing an extension of the periodic Anderson model in the U=infinity limit with a nearest-neighbor attractive interaction between the localized f electrons. We show that higher values of the hybridization parameter imply lower values associated with the maximum of the superconducting critical temperature T-c, indicating that the real charge transfer between bands tends to destabilize the Cooper pairing. Moreover, we show that the superconductivity is constrained to the vicinity of a range of densities where the f-band density of states at the Fermi level rho(f)(mu) has sufficiently high values, and it was found both for configurations where the system presents intermediate-valence and heavy-fermion behaviors, as experimentally observed. Finally, as the total occupation is raised and for large hybridization parameter V there is an insulator-superconductor transition, which is related to the existence of a hybridization gap that cannot be accessed by the slave-boson method, because when the chemical potential lies in or above the gap the system suffers the second-order phase transition characteristic of that method.

【 授权许可】

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