Optical investigations of the chemical pressurized EuFe2(As1-xPx)2: an s-wave superconductor with strong interband interaction

TL;DR

This study uses infrared spectroscopy to analyze EuFe2(As0.82P0.18)2 single crystals, revealing an s-wave superconducting gap and increased interband coupling near the critical temperature.

Contribution

It provides the first detailed optical characterization of EuFe2(As0.82P0.18)2, demonstrating an s-wave gap and enhanced interband interactions in pressurized EuFe2(As1-xPx)2.

Findings

Superconducting gap of 2Δ₀ = 9.5 meV observed below Tc

Optical conductivity matches BCS s-wave superconductor model

Increased interband coupling as temperature approaches Tc

Abstract

Superconducting EuFe2(As0.82P0.18)2 single crystals are investigated by infrared spectroscopy in a wide frequency range. Below Tc=28K a superconducting gap forms at 2\Delta_{0} = 9.5 meV = 3.8 k_B T_c causing the reflectivity to sharply rise to unity at low frequency. In the range of the gap the optical conductivity can be perfectly described by BCS theory with an $s$-wave gap and no nodes. From our analysis of the temperature dependent conductivity and spectral weight at T>T_c, we deduce an increased interband coupling between hole- and electron-sheets on the Fermi surface when $T$ approaches T_c.