Single 20meV boson mode in KFe2As2 detected by point-contact spectroscopy

TL;DR

This study combines experimental point-contact spectroscopy and theoretical calculations to identify a prominent 20meV boson mode in KFe2As2, which could be key to understanding its superconducting properties.

Contribution

It provides the first combined experimental and theoretical analysis revealing a specific boson mode in KFe2As2, highlighting potential non-phononic mechanisms.

Findings

A pronounced 20meV peak in the PC spectrum.

Featureless behavior at energies below and above 20meV.

Discussion of phonon and excitonic origins for the peak.

Abstract

We report an experimental and theoretical investigation of the electron-boson interaction in KFe2As2 by point-contact (PC) spectroscopy, model, and ab-initio LDA-based calculations for the standard electron-phonon Eliashberg function. The PC spectrum viz. the second derivative of the I - V characteristic of representative PC exhibits a pronounced maximum at about 20meV and surprisingly a featureless behavior at lower and higher energies. We discuss phonon and non-phonon (excitonic) mechanisms for the origin of this peak. Analysis of the underlying source of this peak may be important for the understanding of serious puzzles of superconductivity in this type of compounds.