The uncollapsed LaFe2As2 phase: compensated, highly doped, electron-phonon coupled, iron-based superconductor

TL;DR

This study investigates LaFe2As2, a highly doped iron-based superconductor, revealing its normal state properties, electron-phonon coupling, and its bridging role between unconventional and conventional superconductors.

Contribution

It provides detailed experimental insights into the normal state and electron-phonon interactions of LaFe2As2, a highly doped superconductor, highlighting its unique position in superconductor classification.

Findings

Presence of highly compensated electron and hole bands.

High effective masses around 3m0.

Transport properties resemble conventional superconductors.

Abstract

The recently discovered LaFe2As2 superconducting compound, member of the 122 family of iron pnictide superconductors, becomes superconducting below Tc=13K, yet its nominal doping apparently places it in the extreme overdoped limit, where superconductivity should be suppressed. In this work, we investigate the normal state of magneto- and thermo-electric transport and specific heat of this compound. The experimental data are consistent with the presence of highly compensated electron and hole bands, with around 0.42 electrons per unit cell just above Tc, and high effective masses around 3m0. The temperature dependence of transport properties strongly resembles that of conventional superconductors, pointing to a key role of electron-phonon coupling. From these evidences, LaFe2As2 can be regarded as the connecting compound between unconventional and conventional superconductors.