Evidence of nodal superconductivity in LaFeSiH

TL;DR

This study provides evidence of nodal superconductivity in LaFeSiH, a novel iron-based superconductor, through experimental measurements and theoretical analysis, revealing a complex gap structure possibly involving d-wave pairing.

Contribution

It combines muon spin rotation, tunneling diode oscillator, and density functional theory to characterize the superconducting gap and propose a possible d-wave pairing symmetry.

Findings

Magnetic penetration depth shows sub-$T^2$ behavior below $T_c/3$

Evidence of a nodal or deep minima gap structure

Fermi surface features suggest possible d-wave pairing

Abstract

Unconventional superconductivity has recently been discovered in the first iron-based superconducting silicide LaFeSiH. By using the complementary techniques of muon spin rotation, tunneling diode oscillator and density functional theory, we investigate the magnetic penetration depth and thereby the superconducting gap of this novel high-temperature superconductor. We find that the magnetic penetration depth displays a sub-$T^2$ behavior in the low-temperature regime below $T_c/3$, which evidences a nodal structure of the gap (or a gap with very deep minima). Even if the topology of the computed Fermi surface is compatible with the $s_\pm$-wave case with accidental nodes, its nesting and orbital-content features may eventually result in a $d$-wave state, more unusual for high-temperature superconductors of this class.