Distinction between critical current effects and intrinsic anomalies in the point-contact Andreev reflection spectra of unconventional superconductors**Project supported by the National Key Basic Research Program of China (Grant Nos. 2015CB921000, 2016YFA0300301, and 2017YFA0302902), the National Natural Science Foundation of China (Grant Nos. 11674374 and 1474338), the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant No. QYZDB-SSW-SLH008), the

Abstract

In this work, we discuss the origin of several anomalies present in the point-contact Andreev reflection spectra of (Li1−xFex)OHFeSe, LiTi2O4, and La2−xCexCuO4. While these features are similar to those stemming from intrinsic superconducting properties, such as Andreev reflection, electron-boson coupling, multigap superconductivity, d-wave and p-wave pairing symmetry, they cannot be accounted for by the modified Blonder–Tinkham–Klapwijk (BTK) model, but require to consider critical current effects arising from the junction geometry. Our results point to the importance of tracking the evolution of the dips and peaks in the differential conductance as a function of the bias voltage, in order to correctly deduce the properties of the superconducting state.