Magnetic phase separation and superfluid density measurements in alkali metal-organic solvent intercalated iron selenide superconductor Lix(C5H5N)yFe2-zSe2

TL;DR

This study investigates the magnetic and superconducting properties of an intercalated iron selenide superconductor, revealing phase separation and a two-gap s+s-wave superconducting state with unchanged gap symmetry after intercalation.

Contribution

It provides detailed muon-spin spectroscopy analysis showing phase separation and confirms the two-gap superconductivity in intercalated FeSe, maintaining the gap symmetry of the parent compound.

Findings

Nearly half of the sample is magnetically ordered.

Superconductivity described by a two-gap s+s-wave model.

Superconducting gap symmetry remains unchanged after intercalation.

Abstract

We report the low-temperature electronic and magnetic properties of the alkali metal-organic solvent intercalated iron selenide superconductor Lix(C5H5N)yFe2-zSe using muon-spin-spectroscopy measurements. The zero-field \muSR results indicate that nearly half of the sample is magnetically ordered and there is a spatial phase separation between the superconducting and the magnetic fraction. The transverse-field \muSR results show that the temperature dependence of the penetration depth \lambda(T) in the mixed state of Lix(C5H5N)yFe2-zSe can be explained using a two-gap s+s-wave model with gap values of 6.82(92) and 0.93(7) meV. This implies that the symmetry of the superconducting gap in this system remains unaltered to the parent compound FeSe even after the intercalation with the molecular spacer layer. We obtain \lambda (0) = 485(21) nm at T = 0 K.