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

Abstract

We report a mechanical point-contact spectroscopy study on the single crystalline NbGe${}_2$ with a superconducting transition temperature $T{}_{\mathrm{c}}$ = 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{}_{\mathrm{B}}$$T{}_{\mathrm{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.

6 pages and 4 figures

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Cited by in corpus (2)

• Anisotropic superconductivity in ZrB${}_{12}$ near critical Bogomolnyi point
• Absence of diode effect in chiral type-I superconductor NbGe2