Gap-like feature in the normal state of $\bf{X(Fe_{1-x}Co_x)_2As_2}$, $\bf{X=Ba,Sr}$ and $\bf{Fe_{1+y}Te}$ revealed by Point Contact Spectroscopy

TL;DR

Point contact spectroscopy uncovers a gap-like feature in the normal state of iron-based superconductors, appearing above magnetic and structural transition temperatures, suggesting possible nematicity-related phenomena.

Contribution

This study reveals a gap-like feature above transition temperatures in several iron-based compounds, providing new insights into their normal state properties and phase diagram modifications.

Findings

Gap-like feature observed above $T_N$ and $T_S$ in multiple materials

Enhancement in conductance spectrum at high temperatures

Modified phase diagram with gap-like feature above transition temperatures

Abstract

Point contact spectroscopy reveals a gap-like feature above the magnetic and structural transition temperatures for underdoped $Ba(Fe_{1-x}Co_x)_2As_2$, $SrFe_2As_2$ and $Fe_{1+y}Te$. The conductance spectrum starts showing an enhancement at temperatures as high as 177 K for $BaFe_2As_2$ ($T_N$ $\sim$ 132 K) and 250 K for $SrFe_2As_2$ ($T_N$ $\sim$ 192 K). Possible origins for this enhancement are discussed in light of recent experimental claims of nematicity in these materials. We construct a modified phase diagram for Co-doped Ba122 showing a gap-like feature existing above $T_N$ and $T_S$ for the underdoped regime.