31 research outputs found
Effect of disorder on superconductivity in the boson-fermion model
We study how a randomness of either boson or fermion site energies affects
the superconducting phase of the boson fermion model. We find that, contrary to
what is expected for s-wave superconductors, the non-magnetic disorder is
detrimental to the s-wave superconductivity. However, depending in which
subsystem the disorder is located, we can observe different channels being
affected. Weak disorder of the fermion subsystem is responsible mainly for
renormalization of the single particle density of states while disorder in the
boson subsystem directly leads to fluctuation of the strength of the effective
pairing between fermions.Comment: 7 pages, 6 figures. Physical Review B (accepted for publication
Upward curvature of the upper critical field in the Boson--Fermion model
We report on a non-conventional temperature behavior of the upper critical
field () which is found for the Boson-Fermion (BF) model. We show
that the BF model properly reproduces two crucial features of the experimental
data obtained for high- superconductors: does not saturate at
low temperatures and has an upward curvature. Moreover, the calculated upper
critical field fits very well the experimental results. This agreement holds
also for overdoped compounds, where a purely bosonic approach is not
applicable.Comment: 4 pages, 3 figures, revte