Nature and symmetry of the order parameter of the noncentrosymmetric superconductor Li2Pt3B

TL;DR

This paper investigates the superconducting gap symmetry of Li2Pt3B, revealing a likely $s_$ wave with line nodes due to strong correlations and spin fluctuations, resolving previous contradictions about its nature.

Contribution

It introduces a theoretical model considering band structure and Coulomb interactions to predict the $s_$ wave gap symmetry in Li2Pt3B.

Findings

Predicted $s_$ wave gap with line nodes

Strong correlations due to nesting and d-character

Normal spin fluctuations favor singlet pairing

Abstract

The nature and symmetry of the superconducting gap function in the noncentrosymmetric superconductor (NCS) Li2Pt3B, even many years after its discovery, appears to be full of contradictions. In this letter based on the existing band structure calculations we find that owing to the considerable nesting near the Fermi surface and the enhanced d-character of the relevant bands that cross the Fermi level,the system gets somewhat strongly correlated. Considering the effect of the onsite Coulomb repulsion on the pairing potential perturbatively, we extract possible superconducting transition. The strong normal spin fluctuation gives rise to a singlet dominant gap function with accompanying sign change. Thus our theory predicts a $s_\pm$ wave gap function with line nodes as the most promising candidate in the superconducting state.