Thermal Stability of Superconductors

Towards Room-Temperature Superconductivity

“…As shown elsewhere [3], such a drawback ensues from an attractive interaction, assumed to couple electrons together, which is not only at loggerheads with the sign of the Coulomb repulsion, but in addition leads to inconsistencies to be recalled below. Therefore this work is intended at investigating the T c dependence upon the parameters, characterising the motion of electrons correlated together through a repulsive force, in order to devise, within the framework of a two-fluid picture developed elsewhere [3][4][5][6], a single model, valid for all superconductors, including low and high T c materials, as well. This is in marked contrast with the mainstream approach, tending to seek a particular model, dedicated to each superconducting compound [7][8][9].…”

“…In order to reach the hereabove mentioned goal, a historical survey, aimed at identifying the cause of the BCS failure and its far-reaching consequences, is needed. Moreover, it will enable the reader to understand why our previous work [3][4][5][6] is not only unrelated to the mainstream view, but also runs afoul at it. As a matter of fact, the original sin was to purport with no scientific proof whatsoever that the many bound electron state, coming out of the BCS variational calculation [1], conveyed the signature of superconductivity, namely it did sustain persistent currents.…”

“…Likewise, a simple experiment was proposed [4] to validate this conclusion and to bring evidence for the anomalous properties of the Joule effect, taking place in a superconductor. Furthermore it proved gratifying to realize that a prerequisite for a thermodynamically stable superconducting phase, discovered subsequently [6], turned out to be consistent with the above mentioned criterion of superconductivity [4]. The discussion below will take full advantage of this achievement but it could not be overemphasized that our thermodynamical criterion [4] acts as a watershed, distinguishing our work from that of all other authors who, unlike us, never question the BCS assumption of an attractive inter-electron force and in addition disregard the issue of persistent currents.…”

“…1-Thermal stability. -The conduction electrons are taken to comprise [3,4,6] bound and independent electrons, in respective temperature dependent concentration c s (T ), c n (T ), such that c 0 = c s (T ) + c n (T ) , with c 0 being the total concentration of conduction electrons. They are organized, respectively, as a many bound electron [3] (MBE) state, characterised by its chemical potential µ(c s ), and a Fermi gas [10] of Fermi energy E F (T, c n ).…”

“…which expresses [23] that the total free energy F n + E s is minimum at T kept fixed, provided ∂E F ∂cn + ∂µ ∂cs > 0. Noteworthy is that ∂µ ∂cs < 0 has been shown to be a prerequisite for persistent currents [4], thermal equilibrium [3], the Josephson effect [5] and a stable [6] superconducting phase. Likewise, Eq.…”