Macroscopic phase segregation in superconducting K0.73Fe1.67Se2 as seen by muon spin rotation and infrared spectroscopy

TL;DR

This study reveals that K0.73Fe1.67Se2 exhibits macroscopic phase segregation into insulating magnetic and metallic superconducting regions, with similar electronic properties to other iron-based superconductors, using muon spin rotation and infrared spectroscopy.

Contribution

It provides the first combined muon spin rotation and infrared spectroscopy analysis demonstrating phase segregation in K0.73Fe1.67Se2.

Findings

88% insulating magnetic matrix

12% metallic superconducting inclusions

Superconducting properties similar to other iron-based superconductors

Abstract

Using muon spin rotation (\muSR) and infrared spectroscopy we investigated the recently discovered superconductor K0.73Fe1.67Se2 with Tc = 32 K. We show that the combined data can be consistently described in terms of a macroscopically phase segregated state with a matrix of ~88% volume fraction that is insulating and strongly magnetic and inclusions with a ~12% volume fraction which are metallic, superconducting and non-magnetic. The electronic properties of the latter, in terms of the normal state plasma frequency and the superconducting condensate density, appear to be similar as in other iron selenide or arsenide superconductors.