A Penetration Depth Study on Li2Pd3B and Li2Pt3B

TL;DR

This study investigates the penetration depth behavior of two isostructural superconductors, Li2Pd3B and Li2Pt3B, revealing different gap structures and pairing symmetries through low-temperature measurements.

Contribution

It provides the first detailed penetration depth analysis of Li2Pd3B and Li2Pt3B, identifying two-gap behavior in one and line nodes in the other, highlighting their distinct superconducting properties.

Findings

Li2Pd3B exhibits two-gap BCS superconductivity.

Li2Pt3B shows linear temperature dependence indicating line nodes.

Distinct gap structures suggest different pairing mechanisms.

Abstract

In this paper we present a penetration depth study on the newly discovered superconductors Li$_2$Pd$_3$B and Li$_2$Pt$_3$B. Surprisingly, the low-temperature penetration depth $f(T)$ demonstrates distinct behavior in these two isostructural compounds. In Li$_2$Pd$_3$B, $f(T)$ follows an exponential decay and can be nicely fitted by a two-gap BCS superconducting model with a small gap $\delta_1=3.2$K and a large gap $\delta_2=11.5$K. However, linear temperature dependence of $f(T)$ is observed in Li$_2$Pt$_3$B below 0.3$T_c$, giving evidence of line nodes in the energy gap.