Full superconducting gap and type-I to type-II superconductivity transition in single crystalline NbGe2

We report a mechanical point-contact spectroscopy study on the single crystalline NbGe2 with a superconducting transition temperature T-c = 2.0-2.1 K. The differential conductance curves at 0.3 K can be well fitted by a single-gap s-wave Blonder-Tinkham-Klapwijk model and the temperature-dependent gap follows a standard Bardeen-Cooper-Schrieffer behavior, yielding Lambda(0) similar to 0.32 meV and 2 Lambda(0)/k(B)T(c) = 3.62 in the weak-coupling limit. In magnetic field, the superconducting gap at 0.3 K remains constant up to H-c1 similar to 150 Oe and gradually decreases until H-c2 similar to 350 Oe, indicating NbGe2 is going through a transition from a type-I to type-II (possible type-II/1) superconductor at low temperature.

Automated summary

In this study, mechanical point-contact spectroscopy was conducted on single crystalline NbGe2 with a superconducting transition temperature Tc = 2.0-2.1 K. The results suggest that NbGe2 may undergo a transition from a type-I to type-II (possible type-II/1) superconductor at low temperatures.