Non-BCS Temperature Dependence of Energy Gap in Thin Film Electron-Doped Cuprates

Abstract

We investigate the dependence of the energy gap (G) on the temperature (T ) for the electron-doped hightemperature superconductors. The following compounds, in the form of the thin films, have been taken into consideration: La 2−x Ce x CuO 4 (LCCO), Pr 2−x Ce x CuO 4 (PCCO), and Nd 2−x Ce x CuO 4 (NCCO). It was found that G(T ) deviates from the BCS prediction more, if a concentration of cerium assumes the lower values. For the lowest concentration (in the case of LCCO and NCCO), the function G (T ) is not quite like the BCS curve, which is connected with the existence of the residual Nernst region. Next, it has been pointed out that the NCCO superconductor becomes structurally unstable for the maximum concentration of cerium, which is leading to the anomalous dependence of the energy gap on the temperature and the induction of the wide Nernst region.

Theoretical investigation of the impact of intra‐ and inter‐layer coupling of high TC superconductor Nd2‐xCexCuO4

“…Variation of Δ as a function of temperature for different doping ( x ) values for superconductor Nd 2‐x Ce x CuO 4 . [ 29–32 ] …”

“…The amplitude of Δ which reflects the formation of electron pairs is an essential measure of the intensity of SC F I G U R E 5 Variation of Δ as a function of temperature for different doping (𝑥) values for superconductor Nd 2-x Ce x CuO 4 . [29][30][31][32] which is quantitatively calculated as a function of temperature as given in Equation (70). Figure 5 shows the variation of Δ with temperature for different doping values (x).…”

The Symmetry of Pairing and the Electromagnetic Properties of a Superconductor with a Four-Fermion Attraction at Zero Temperature

“…We suspect that the four-electron term would appear in the second order of this expansion. One needs to mention that the problem of the four-fermion interaction in superconductors was investigated in a series of papers by Szczȩśniak et al [14][15][16]. In some of them, the Eliashberg formalism was applied in order to deal with cuprates as systems with strong coupling of electrons to phonons.…”

Diagram of the Critical Temperature—Nernst Temperature for the Superconductivity Induced by Modified Electron-Phonon Interaction

“…Nowadays, the four-fermion interaction is also considered in the works [26][27][28], where there is suggested its significant meaning in the description of the high-temperature superconducting state. In relation to the classical electron-phonon interaction taking into account the additional term of the EEPh type causes that it is possible to explain the anomalously high values of the energy gap, the weak dependence of the energy gap on the temperature, and the existence of the Nernst temperature (T ) [17][18][19][29][30][31][32][33][34][35].…”