BCS theory with the external pair potential

Abstract

-b Metrolohichna str. Kiev-03680, Ukraine.We consider a hypothetical substance, where interaction between (within) structural elements of condensed matter (molecules, nanoparticles, clusters, layers, wires etc.) depends on state of Cooper pairs: an additional work must be made against this interaction to break a pair. Such a system can be described by BCS Hamiltonian with the external pair potential term. In this model the potential essentially renormalizes the order parameter: if the pairing lowers energy of the structure the energy gap is slightly enlarged at zero temperature and asymptotically tends to zero as temperature rises. Thus the critical temperature of such a superconductor is equal to infinity formally. For this case the effective Ginzburg-Landau theory is formulated, where the coherence length decreases as temperature rises, the GL parameter and the second critical field are increasing functions of temperature unlike the standard theory. If the pairing enlarges energy of the structure then suppression of superconductivity and the first order phase transition occur.

The role of electron–vibron interaction and local pairing in conductivity and superconductivity of alkali-doped fullerides

“…In a work [12] the model of a hypothetical superconductor has been proposed. In this model an interaction energy between (within) structural elements of condensed matter (molecules, nanoparticles, clusters, layers, wires etc.)…”

“…Based on the alkali-doped fulleride we have proposed realization of the model of superconductivity with the external pair potential formulated in [12]. In this model the potential essentially renormalizes the order parameter so that if the pairing lowers the energy of the molecular structure, then the energy gap tends to zero asymptotically as 1/T with increasing of temperature -Eq.…”

“…Obtained results can be used for increase of the critical temperature. In the Section III based on the alkali-doped fullerides we propose hypothetical material for realization of model of superconductivity with the external pair potential formulated in work [12]. In this model the energy gap tends to zero asymptotically as 1/T with increasing of temperature.…”