Abstract
The heavy fermion system (HFS) is described by the periodic Anderson model (PAM), treating the Coulomb correlation between the f-electrons in the meanfield Hartree-Fock approximation. Superconductivity is introduced by a BCS-type pairing term among the conduction electrons. Within this approximation the equation for the superconducting gap is derived, which depends on the effective position of the energy level of the f-electrons relative to the Fermi level. The latter in turn depends on the occupation probability n f of the f-electrons. The gap equation is solved self-consistently with the equation for n f; and their temperature dependences are studied for different positions of the bare f-electron energy level, with respect to the Fermi level. The dependence of the superconducting gap on the hybridization leads to a re-entrant behaviour with increasing strength. The induced pairing between the f-electrons and the pairing of mixed conduction and f-electrons due to hybridization are also determined. The temperature dependence of the hybridization parameter, which characterizes the number of electrons with mixed character and represents the number of heavy electrons is studied. This number is shown to be small. The quasi-particle density of states (DOS) shows the existence of a pseudo-gap due to superconductivity and the signature of a hybridization gap at the Fermi level. For the choice of the model parameters, the DOS shows that the HFS is a metal and undergoes a transition to the gap-less superconducting state.
Similar content being viewed by others
References
P Wachter, Handbook on the physics and chemistry of rare earths edited by K A Gschneidner, L Eyring Jr, G H Lander and G R Chappin (Elsevier, Amsterdam, 1994) vol. 19, p. 177
C Geibel, S Thies, D Kaczorowski, A Mehner, A Grauel, B Seidel, U Ahlheim, R Helfrich, K Petersen, C D Bredl and F Steglich, Z. Phys. B83, 305 (1991)
C Geibel, C Schank, S Thies, H Kitazawa, C D Bredl, A Böhm, M Rau, A Grauel, R Caspary, R Helfrich, U Ahlheim, G Weber and F Steglich, Z. Phys. B84, 1 (1991)
N K Sato, N Aso, K Miyake, R Shilina, P Thalmeier, G Varel ogiannis, C Geibel, F Steglich, P Fulde and T Komatsubara, Nature (London) 410 340 (2001)
N Metoki, Y Haga, Y Koike and Y Ōnuki, Phys. Rev. Lett. 80(24), 5417 (1998)
G Aeppli and C Broholm, Handbook on the physics and chemistry of rare earths edited by K A Gschneider, L Eyring Jr, G H Lander and G R Choppin (Elsevier Science Publishers B V, Amsterdam, 1994) vol. 19, chap. 131, p. 123
M Jourdan, M Huth, J Hessert and H Adrian, Physica B230–232, 335 (1997)
M Kyogaku, Y Kitaoka, K Asayama, C Geibel, C Schank and F Steglich, J. Phys. Soc. Jpn. 61, 2660 (1992)
H Tou, Y Kitaoka, K Asayama, C Geibel, C Schank and F Steglich, J. Phys. Soc. Jpn. 64, 725 (1995)
K Matsuda, Y Kohori and T Kohara, Phys. Rev. B55, 15223 (1997)
M Sigrist and K Ueda, Rev. Mod. Phys. B63, 239 (1991)
G C Rout and S Das, Physica C339, 17 (2000)
G A Gehring and L E Major, J. Phys. Condens. Matter 6, 495 (1994)
G C Rout and S Das, Solid State Commun. 109, 177 (1999)
G C Rout, S Das and S N Behera, Physica C371, 185 (2002)
D N Zubarev, Sov. Phys. Usp. 3, 320 (1960)
S N Behera, B N Panda, G C Rout and P Entel, Int. J. Mod. Phys. B19–20, 2519 (2001)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rout, G.C., Ojha, M.S. & Behera, S.N. Superconducting gap anomaly in heavy fermion systems. Pramana - J Phys 70, 711–730 (2008). https://doi.org/10.1007/s12043-008-0032-1
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12043-008-0032-1