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Boris V. Vasiliev Supercondustivity Superfluidity

Superconductivity and

Superconductivity and Superfluidity The comparison of the calculated parameters and measured data ([22], [32]) is given in Table 7.1-7.2 and in Figure 7.1 and 8.1. 7.2 The Relation of Critical Parameters of Type-I Superconductors The phenomenon of condensation of zero-point oscillations in the electron gas has its characteristic features. There are several ways of destroying the zero-point oscillations condensate in electron gas: Firstly, it can be evaporated by heating. In this case, evaporation of the condensate should possess the properties of an order-disorder transition. Secondly, due to the fact that the oscillating electrons carry electric charge, the condensate can be destroyed by the application of a sufficiently strong magnetic field. For this reason, the critical temperature and critical magnetic field of the condensate will be interconnected. This interconnection should manifest itself through the relationship of the critical temperature and critical field of the superconductors, if superconductivity occurs as result of an ordering of zero-point fluctuations. Let us assume that at a given temperature T < T c the system of vibrational levels of conducting electrons consists of only two levels: • firstly, basic level which is characterized by an anti-phase oscillations of the electron pairs at the distance Λ 0 /2, and • secondly, an excited level characterized by in-phase oscillation of the pairs. Let the population of the basic level be N 0 particles and the excited level has N 1 particles. 78 Science Publishing Group

Chapter 7 The Condensate of Zero-Point Oscillations and Type-I Superconductors Two electron pairs at an in-phase oscillations have a high energy of interaction and therefore cannot form the condensate. The condensate can be formed only by the particles that make up the difference between the populations of levels N 0 −N 1 . In a dimensionless form, this difference defines the order parameter: Ψ = N 0 N 1 − . (7.5) N 0 + N 1 N 0 + N 1 In the theory of superconductivity, by definition, the order parameter is determined by the value of the energy gap Ψ = ∆ T /∆ 0 . (7.6) When taking a counting of energy from the level ε 0 , we obtain ∆ T ∆ 0 = N 0 − N 1 N 0 + N 1 ≃ e2∆ T /kT − 1 e 2∆ T /kT + 1 = th(2∆ T /kT ). (7.7) Passing to dimensionless variables δ ≡ ∆ T ∆ 0 , t ≡ kT kT c and β ≡ 2∆0 kT c we have δ = eβδ/t − 1 = th(βδ/t). (7.8) e βδ/t + 1 This equation describes the temperature dependence of the energy gap in the spectrum of zero-point oscillations. It is similar to other equations describing other physical phenomena, that are also characterized by the existence of the temperature dependence of order parameters [43], [44]. For example, this dependence is similar to temperature dependencies of the concentration of the superfluid component in liquid helium or the spontaneous magnetization of ferromagnetic materials. This equation is the same for all order-disorder transitions (the phase transitions of 2nd-type in the Landau classification). The solution of this equation, obtained by the iteration method, is shown in Figure 7.2. Science Publishing Group 79

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