Pressure-Dependent Point-Contact Spectroscopy of Superconducting PbTaSe2 Single Crystals

We develop an experimental tool to investigate the order parameter of superconductors by combining pointcontact spectroscopy measurement with high-pressure technique.It is demonstrated for the first time that planar point-contact spectroscopy measurement on noncentrosymmetric superconducting PbTaSe2 single crystals is systematically subjected to hydrostatic pressures up to 12.1 kbar.Under such a high pressure,the normal-state contact resistance is sensitive to the applied pressure,reflecting the underlying variation of contact transparency upon pressures.In a superconducting state,the pressure dependence of the energy gap△0 and the critical temperature Tc for gap opening/closing are extracted based on a generalized Blond-Tinkham-Klapwijk model.The gap ratio 2△0/kB Tc indicates a crossover from weak coupling to strong coupling in electron pairing strength upon pressure for PbTaSe2.Our experimental results show the accessibility and validity of high-pressure pointcontact spectroscopy,offering rich information about high-pressure superconductivity.

Tip-induced superconductivity commonly existing in the family of transition-metal dipnictides MPn_(2)

We report the tip-induced superconductivity on the topological semimetal NbSb_(2), similar to the observation on TaAs_(2) and NbAs_(2). Belonging to the same family of MPn_(2), all these materials possess similar band structures, indicating that the tip-induced superconductivity may be closely related to their topological nature and share a common mechanism. Further analysis suggests that a bulk band should play the dominant role in such local superconductivity most likely through interface coupling. In addition, the compatibility between the induced superconductivity and tips’ ferromagnetism gives an evidence for its unconventional nature. These results provide further clues to elucidate the mechanism of the tip-induced superconductivity observed in topological materials.

Anisotropic interfacial superconductivity induced at point contacts on topological semimetal grey arsenic

The origin of superconductivity observed at the point contact between the normal metal tip and the topological material remains uncertain due to the potential presence of superconducting elements or allotropes impurities.It is imperative to seek out a topological material entirely free of superconducting impurities and induce superconductivity between it and normal tips to verify the source of the induced superconductivity.Here,we report the observation of superconductivity up to 9 K induced at point contacts between normal metal tips and the topological material grey arsenic,which is free of superconductivity.The determined temperature dependencies of superconducting gapsΔ(T)deviate from the Bardeen-Cooper-Schriefer(BCS)superconductivity law,exhibiting abnormal behavior.Furthermore,the highly anisotropic upper critical field H_(c2)(T)suggests the anisotropy of the projected interfacial Fermi surface.By tuning the junction resistance,we obtained a negative correlation between the superconducting gapΔand the efective barrier height Z,which validates the interfacial coupling strength as a key factor in the observed tip-induced superconductivity.These experimental results provide guidance for the relevant theory about tip-induced superconductivity on topological materials.