Two-gap superconductivity in the noncentrosymmetric La$_3$Se$_4$ compound

TL;DR

This study investigates the noncentrosymmetric La$_3$Se$_4$ superconductor, revealing evidence of two-gap superconductivity through spectroscopy, heat capacity, and magnetization measurements, with implications for understanding unconventional superconducting states.

Contribution

The paper provides direct experimental evidence of two-gap superconductivity in La$_3$Se$_4$, combining spectroscopy with thermodynamic and magnetic measurements to characterize its unconventional pairing mechanism.

Findings

Observation of two distinct superconducting gaps.

Temperature and magnetic field dependence support two-gap structure.

Consistent results from spectroscopy, heat capacity, and magnetization.

Abstract

Point-contact Andreev reflection spectroscopy at low temperatures and high magnetic fields has been performed on a noncentrosymmetric La$_3$Se$_4$ superconductor with a critical temperature $T_c$ = 8 K. Two superconducting energy gaps $\Delta_1$ and $\Delta_2$ with $2\Delta_{1}/k_{B} T_{c}$ ~ 5.8 and $2\Delta_{2}/k_{B} T_{c}$ ~ 2.3, are directly observed in some of the spectra. The temperature and magnetic field effects help to resolve a two-gap structure even on the most frequent spectra where at low temperatures only a single gap is apparent, reflected in a pair of maxima around the zero bias. Two-gap superconductivity consistently with the point contact Andreev reflection spectroscopy is also supported by the heat capacity and the Hall probe magnetization measurements.