Effects of Pressure on the Superconducting Transition Temperatures of Sn, In, Ta, Tl, and Hg

High Pressure Effects on Superconductivity

“…the lattice transformation is suppressed down to the superconducting state. The structural transition was theoretically described within the WegerLabbé-Friedel (WLF) linear-chain model [36] and it was shown that good agreement with the experimentally derived pressure coefficient dT L /dp was only obtained for V 3 Si when the interband charge transfer under pressure was properly taken into account [37]. The calculation shows that the pressure effect on the electronic structure and the pressure-induced charge transfer from s to d-bands are essential to explain the experimental data.…”

“…The critical temperature of thallium was found to increase at low pressures. It passes through a maximum at about 0.2 GPa and decreases at higher p [3,4]. Since no structural transition was observed under pressure it was suspected that the unusual T c (p) dependence might be due to a modification of the electronic configuration under pressure [4].…”

“…The main difficulty at the time was the limited experimentally accessible pressure range of several GPa and the need to extrapolate the experimental data of T c (p) to much higher pressures to estimate the T c =0 intercept. In many cases T c (p) turned out to be a nonlinear function of p at higher pressures, however, it was proposed [3] that T c was roughly linear when plotted as function of volume, V. The linear T c (V) relationship was later shown to hold for a large number of superconducting metals and the critical pressures above which superconductivity cannot persist have been derived from a linear extrapolation of T c (V) [18]. An impressive example of this linear T c vs. V relation is shown in Fig.…”

“…Some A15 compounds, such as V 3 Si, are weakly coupled BCS-like superconductors but others (e.g. Nb 3 Sn, Nb 3 Ge) exhibit strong electron-phonon coupling and are better described by the strong-coupling theory.…”

“…Some A15 compounds, such as V 3 Si, are weakly coupled BCS-like superconductors but others (e.g. Nb 3 Sn, Nb 3 Ge) exhibit strong electron-phonon coupling and are better described by the strong-coupling theory. A number of A15 compounds undergo a structural phase transition at T L > T c from the high-temperature cubic phase to a low-temperature tetragonal phase (although the tetragonal distortion is very small).…”