“Break-junction” technique in application to layered superconductors (Review Article)

Abstract

A comprehensive study of superconductor-constriction-superconductor contacts, obtained using the “break-junction” technique in layered superconductors. Depending on the constriction transparency, tunneling and SnS Andreev spectroscopies could be used to directly determine the values of the superconducting gaps, characteristic BCS ratios and temperature dependences of the gaps in cuprates, magnesium diboride and iron pnictides and chalcogenides. Based on these results we can estimate the gap anisotropy and the electron-boson coupling constants. The advantages and drawbacks of “break-junction” technique are discussed, and we demonstrate that this method is powerful enough for the study of optical phonon modes in high-temperature superconducting cuprates and for creating contacts with selective transparency in Mg1-xAlxB2 compounds.