The Upper Critical Field and the Density of States in Amorphous Superconductors

  • G. Bergmann


A number of superconductors can be obtained in the amorphous state by quenched condensation onto a substrate at He temperature.1 The specific resistance of these amorphous metals is almost identical to the resistance of the corresponding liquid metals. It was shown by electron diffraction 2–4 that the ordering range is not longer than a few atoms, just as in the liquid metals. For several reasons it is rather interesting to measure the upper critical field of the amorphous superconductors. First, the mean free path of the electrons is of the order of atomic distances. Therefore we expect rather large critical fields B c2 . Second, the amorphous superconductors are strong coupling5 and we want to look for strong coupling effects in the temperature behavior of B c2 . Third, the initial slope of the B c2 (T) curve yields the density of states at the Fermi surface
$$N=\frac{\pi }{4}\frac{d{{B}_{c2}}/dT}{{{K}_{B}}e\rho }$$
where kB is the Boltzmann constant, e is the elementary charge, and ρ is the residual resistivity.


Liquid Metal Fermi Surface Critical Field Initial Slope Transition Curve 
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Copyright information

© Springer Science+Business Media New York 1974

Authors and Affiliations

  • G. Bergmann
    • 1
  1. 1.Institut für FestkörperforschungKernforschungsanlage JülichGermany

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