Superconductivity and Superfluidity This estimation of the relationship ∆ 0 /kT c obtained for condensate has a satisfactory agreement with the measured data [32]. 2 Table 7.5 The value of ratio ∆ 0/kT c obtained experimentally for type-I superconductors. superconductor T c,K ∆ 0,mev ∆ 0 kT c Cd 0.51 0.072 1.64 Zn 0.85 0.13 1.77 Ga 1.09 0.169 1.80 Tl 2.39 0.369 1.79 In 3.41 0.541 1.84 Sn 3.72 0.593 1.85 Hg 4.15 0.824 2.29 Pb 7.19 1.38 2.22 2 In the BCS-theory ∆ 0 kT c ≃ 1.76. 90 Science Publishing Group
Chapter 8 Another Superconductors 8.1 About Type-II Superconductors In the case of type-II superconductors the situation is more complicated. In this case, measurements show that these metals have an electronic specific heat that has an order of value greater than those calculated on the base of free electron gas model. The peculiarity of these metals is associated with the specific structure of their ions. They are transition metals with unfilled inner d-shell (see Table 8.1). It can be assumed that the increase in the electronic specific heat of these metals should be associated with a characteristic interaction of free electrons with the electrons of the unfilled d-shell. Since the heat capacity of the ionic lattice of metals is negligible at low temperatures, only the electronic subsystem is thermally active.
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