Scanning Tunneling Spectroscopy on SrFe$\mathrm{_2}$(As$\mathrm{_{1-x}}$P$\mathrm{_x}$)$\mathrm{_2}$

TL;DR

This study uses scanning tunneling spectroscopy to analyze the superconducting and magnetic phases of SrFe$_2$(As$_{1-x}$P$_x$)$_2$ single crystals, revealing a nodal superconducting gap and bosonic excitations.

Contribution

First detailed tunneling spectroscopy investigation of SrFe$_2$(As$_{1-x}$P$_x$)$_2$ across different phases, identifying nodal gaps and bosonic modes.

Findings

Superconducting gap exhibits V-shape, indicating nodal superconductivity.

Superconducting coherence length measured via spatially resolved DOS.

Bosonic excitations observed and discussed in relation to phonon and non-phonon mechanisms.

Abstract

We investigated SrFe$\mathrm{_2}$(As$\mathrm{_{1-x}}$P$\mathrm{_x}$)$\mathrm{_2}$ single crystals with four different phosphorus concentrations x in the superconducting phase (x = 0.35, 0.46) and in the magnetic phase (x = 0, 0.2). The superconducting samples display a V-shaped superconducting gap, which suggests nodal superconductivity. Furthermore we determined the superconducting coherence length by measuring the spatially resolved superconducting density of states (DOS). Using inelastic tunneling spectroscopy we investigated excitations in the samples with four different phosphorus concentrations. Inelastic peaks are related to bosonic modes. Phonon and non-phonon mechanism for the origin of these peaks are discussed.