Time of life as it is in LiFeAs

TL;DR

This study measures quasiparticle lifetimes in LiFeAs using ARPES, revealing two energy scales linked to phonons and electron-electron interactions, supporting phonon-mediated superconductivity with enhanced density of states.

Contribution

It provides the first direct measurement of quasiparticle lifetimes in LiFeAs, highlighting the roles of phonons and electron-electron interactions in its superconductivity.

Findings

Identification of two energy scales: phonon-related and electron-electron interactions.

Evidence supporting phonon-mediated pairing mechanism in LiFeAs.

Observation of strongly enhanced electronic density of states at the Fermi level.

Abstract

The time of life of fermionic quasiparticles, the distribution of which in the momentum-energy space can be measured by angle resolved photoemission (ARPES), is the first quantity to look for fingerprints of interaction responsible for the superconducting pairing. Such an approach has been recently used for superconducting cuprates, but its direct application to pnictides was not possible due to essential three-dimensionality of the electronic band structure and magnetic ordering. Here, we report the investigation of the quasiparticle lifetime in LiFeAs, a non-magnetic stoichiometric superconductor with a well separated two-dimensional band. We have found two energy scales: the lower one contains clear fingerprints of optical phonon modes while the higher scale indicates a presence of strong electron-electron interaction. The result suggests that LiFeAs is a phonon mediated superconductor with strongly enhanced electronic density of states at the Fermi level.