Study of Fermi-Surface Topology Changes in Rhenium and Dilute Re Solid Solutions fromTcMeasurements at High Pressure

Pressure‐induced optical phonon self‐energy changes in rhenium metal

“…2(c) indicate that this effect takes place already at pressures below 3 GPa. This would be consistent with earlier indications of Fermi surface topology changes at relatively low pressures [8].…”

“…However, an anomaly in the pressure dependence of the superconducting transition temperature of Re [8] has been interpreted as a manifestation of Fermi surface topology changes occurring at a relatively low pressures (up to 1.6 GPa). Therefore, one may expect that pressure-induced changes of the electronic structure near E F may also affect the low-temperature phonon parameters.…”

High Pressure Effects on Superconductivity

“…At Os concentrations in excess of 2.75 % the pressure dependence of T c is close to linear and can be considered as "normal". A similarly strong effect was observed in Re-W alloys but, in contrast to the Re-Os alloy, the critical pressure defined by the minimum of T c (p) increased quickly with the tungsten concentration [32]. This qualitatively different behavior can be understood by taking in mind that Os adds one electron thus raising the Fermi energy whereas W decreases the number of electrons and lowers E F .…”

“…T c of Re first decreases at low pressure, passes through a minimum close to 0.7 GPa, and increases slightly above this pressure. T c (p) measured for a Re singlecrystal [32] is shown in Fig. 2.…”

“…A more detailed discussion of the topological changes of the Fermi surface that will appear if the Fermi energy passes through critical points in the reciprocal space and its relation to the nonlinear component of T c (p) is given in Ref. [32]. It should be noted that a band structure calculation for rhenium [33] revealed the existence of such critical points near the Fermi surface and provided evidence for the change of Fermi surface topology similar to that discussed above when the Fermi Energy is raised.…”