# Probing the superconducting gap structure of (Li$_{1-x}$Fe$_x$)OHFeSe

## TL;DR

This study investigates the superconducting gap structure of (Li$_{1-x}$Fe$_x$)OHFeSe using penetration depth measurements, revealing a fully gapped superconductor with complex multi-gap or anisotropic characteristics.

## Contribution

It provides the first detailed analysis of the gap structure in (Li$_{1-x}$Fe$_x$)OHFeSe, suggesting multi-gap or anisotropic superconductivity.

## Key findings

- Nearly temperature-independent $ riangle\lambda(T)$ indicating a fully open gap
- Superfluid density data inconsistent with single-gap isotropic s-wave model
- Evidence supports two-gap, orbital selective, or anisotropic s-wave models

## Abstract

We report measurements of the London penetration depth [$\Delta\lambda(T)$] of the recently discovered iron-based superconductor (Li$_{1-x}$Fe$_x$)OHFeSe, in order to characterize the nature of the superconducting gap structure. At low temperatures, $\Delta\lambda(T)$ displays nearly temperature independent behavior, indicating a fully open superconducting gap. We also analyze the superfluid density $\rho_s(T)$ which cannot be well accounted for by a single-gap isotropic $s$-wave model but are consistent with either two-gaps, a model for the orbital selective $s\times\tau_3$ state or anisotropic $s$-wave superconductivity.