Type I Superconductivity in YbSb2 Single Crystals

TL;DR

This paper reports the discovery of type I superconductivity in YbSb2 single crystals, characterized by low critical temperature and field, confirmed through multiple measurement techniques, and suggests a possible second superconducting state.

Contribution

First demonstration of type I superconductivity in YbSb2, with detailed characterization and evidence of a second superconducting state at lower temperature.

Findings

Critical temperature approximately 1.3 K

Critical field approximately 55 Oe

Evidence of a second superconducting state around 0.41 K

Abstract

We present evidence of type I superconductivity in YbSb2 single crystals, from DC and AC magnetization, heat capacity and resistivity measurements. The critical temperature and critical field are determined to be $T_c\approx$ 1.3 K and $H_c\approx$ 55 Oe. A small Ginzburg-Landau parameter \kappa = 0.05, together with typical magnetization isotherms of type I superconductors, small critical field values, a strong Differential Paramagnetic Effect (DPE) signal, and a field-induced change from second to first order phase transition, confirm the type I nature of the superconductivity in YbSb2. A possible second superconducting state is observed in the radiofrequency (RF) susceptibility measurements, with $T_{c}^{(2)}\approx$ 0.41 K and $H_{c}^{(2)}\approx$ 430 Oe.