Intercalate Superconductivity and van der Waals Equation

Abstract

Superconductivity in two single-element intercalated compounds has been investigated with the van der Waals equation. For Cu x TiSe 2 and YBa 2 Cu 3 O 6+ x , the van der Waals term characterizing the attractive energy per particle (i.e., electrons), aN / V , is calculated from concentration-dependent transition temperature plots derived from experiment. It is shown that two times the attractive energy per intercalant valence electron (2 aN val / V unit ) is equal to the energy gap predicted by BCS theory (Δ) for these superconductors. This realization allows another way to estimate the energy gap of superconducting intercalated insulators and semiconductors, this time, directly from physical real-space properties of the superconductor and the applied external pressure. The physical properties of importance are shown to be the intercalant concentration, transition temperature, and the number of intercalant valence electrons per unit cell volume.

Microstructure, magnetoresistivity and carrier mobility of HTSC-YBCO tape with pinning centers generated by electron irradiation

“…While XRD and Hall methods keep the sample tape integrity and distinguish various nanophases related to PC occurring above Tc (90 K) in a mixed state. It is due to topological defects in intercalated YBCO, where vortex dynamics behave as the ideal gas [13][14][15], so it differs from the mobility of current carriers in the normal conductors, as calculated by the Hall method. Simultaneous measurements of magnetoresistance and carrier mobility allow reveal phase transitions from the normal metal to the mixed state and then to the superconducting state, which characterize HTSC-YBCO of the 2-nd type.…”