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arXiv · 2106.14419

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

Dongting Zhang·Tian Le·Baijing Lv·Lichang Yin·Chufan Chen·Zhiyong Nie·Dajun Su·Huiqiu Yuan·Zhu-An Xu·Xin Lu
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Abstract

We report a mechanical point-contact spectroscopy study on the single crystalline NbGe$_2$ with a superconducting transition temperature $T\rm_c$ = 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 $\Delta_0 \sim$ 0.32 meV and 2$\Delta_0$/$k\rm_{B}$$T\rm_{c}$ = 3.62 in the weak coupling limit. In magnetic field, the superconducting gap at 0.3 K keeps constant up to $H_{c1}\sim$150 Oe and gradually decreases until $H_{c2}\sim$350 Oe, indicating NbGe$_2$ going through a transition from type-I to type-II (possible type-II/1) superconductor at low temperature.

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Dongting Zhang, Tian Le, Baijing Lv, Lichang Yin, Chufan Chen, Zhiyong Nie, Dajun Su, Huiqiu Yuan, Zhu-An Xu, Xin Lu. 2021-06-28. Full superconducting gap and type-I to type-II superconductivity transition in single crystalline NbGe2. https://doi.org/10.1103/physrevb.103.214508

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