Tunneling spectroscopy of the <i>α</i>-and <i>β</i>-phases of In–Sn alloys and hydrostatically compressed indium
Abstract
It is shown that tin impurities enhance while pressure weakens the superconducting properties and electron–phonon interaction in indium. The changes in the critical temperature in the α-phase of In–Sn alloys and in In under pressure are due primarily to changes in the lattice, while those in the β-phase are caused by a strong increase in the electronic parameter. The differences in the behavior of the Van Hove singularities in the phonon spectrum ωi, of the alloys and indium under pressure stem from the differences in the crystal structure deformations. The nonlinear changes in the superconducting parameters and frequencies ωi, at low impurity concentrations (2 at.% Sn) or under 6 kbar pressure are due to topological transitions in the Fermi surface of In, which causes lattice instability as a result of the electron–phonon interaction. This is the origin of the α ⇄ β phase transition.