Non-centro-symmetric superconductors Li2Pd3B and Li2(Pd0.8Pt0.2)3B: amplitude and phase fluctuations analysis of the experimental magnetization data

TL;DR

This study investigates the magnetization behavior of two non-centro-symmetric superconductors, revealing mean field transition in one and phase fluctuation effects in the other, highlighting the impact of non s-wave pairing and critical fluctuations.

Contribution

It provides the first detailed analysis of amplitude and phase fluctuations in Li2Pd3B and Li2(Pd0.8Pt0.2)3B superconductors using experimental magnetization data.

Findings

Li2Pd3B exhibits mean field superconducting transition.

Li2(Pd0.8Pt0.2)3B shows significant phase fluctuations.

Critical fluctuations dominate above Tc in the Pt-containing compound.

Abstract

We report on magnetization data obtained as a function of temperature and magnetic field in Li2 (Pd0.8Pt0.2)3B and Li2Pd3B non-centro-symmetric superconductors. Reversible magnetization curves were plotted as M1/2 vs. T. This allows study of the asymptotic behavior of the averaged order parameter amplitude (gap) near the superconducting transition. Results of the analysis show, as expected, a mean field superconducting transition for Li2Pd3B. On contrary, a large deviation from the mean field behavior is revealed for Li2(Pd0.8Pt0.2)3B. This is interpreted as due to the strength of the non s-wave spin-triplet pairing in this Pt-containing compound which produces nodes in the order parameter and consequently, phase fluctuations. The diamagnetic signal above Tc(H) in Li2Pd3B is well explained by superconducting Gaussian fluctuations, which agrees with the observed mean field transition. For Li2(Pd0.8Pt0.2)3B the diamagnetic signal above Tc(H) is much higher than the expected Gaussian values and appears to be well explained by three dimensional critical fluctuations of the lowest-Landau-level type, which somehow agrees with the scenario of a phase mediated transition.