Pseudogap in the electronic density of states of superconducting glasses |
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Authors: | R Oppermann |
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Institution: | (1) Service de Physique Théorique, CEN Saclay, F-91191 Gif-sur-Yvette, France |
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Abstract: | Two loop order results for the electronic density of states (DOS) of both Ising- and XY-type superconducting glass phases are presented. Maximal depression of the DOS by critical fluctuation corrections to its finite mean field value is found to occur at the Fermi energyE
F
. The theory is renormalizable and exponentiation of the loop expansion yields (E
F)=0 for the DOS in two dimensions and for arbitrarily small disorder. It is also concluded that the DOS assumes nonzero values, when either |E–E
F|, or magnetic field H, or temperature T become nonzero. A pseudogap (atT=0,H=0) or a smeared gap (forH 0 orT 0) is thus obtained with a DOS-minimum at the Fermi level. A rough estimate of the effective width is given. In three dimensions, the DOS atE
F vanishes like (n
c
I
–n)1/2 for the Ising-type glass and like (n
c
XY
–n)1 for the XY-type glass as the impurity concentrationn exceeds characteristic values. At second loop order, the calculation contains a nontrivial indication of a lower critical dimension two. |
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Keywords: | |
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