In-plane electronic anisotropy of underdoped "122" Fe-arsenide superconductors revealed by measurements of detwinned single crystals

TL;DR

This paper reviews recent experimental findings on the intrinsic in-plane electronic anisotropy in underdoped '122' Fe-arsenide superconductors, highlighting the role of the nematic phase transition in their electronic properties.

Contribution

It provides a comprehensive review of experimental techniques and results revealing electronic anisotropy and nematic order in detwinned single crystals of underdoped Fe-arsenide superconductors.

Findings

Detection of in-plane electronic anisotropy through resistivity, reflectivity, and ARPES measurements.

Evidence supporting the existence of an Ising nematic phase transition.

Correlation between structural transition and electronic anisotropy in the '122' family.

Abstract

The parent phases of the Fe-arsenide superconductors harbor an antiferromagnetic ground state. Significantly, the N\'eel transition is either preceded or accompanied by a structural transition that breaks the four fold symmetry of the high-temperature lattice. Borrowing language from the field of soft condensed matter physics, this broken discrete rotational symmetry is widely referred to as an Ising nematic phase transition. Understanding the origin of this effect is a key component of a complete theoretical description of the occurrence of superconductivity in this family of compounds, motivating both theoretical and experimental investigation of the nematic transition and the associated in-plane anisotropy. Here we review recent experimental progress in determining the intrinsic in-plane electronic anisotropy as revealed by resistivity, reflectivity and ARPES measurements of detwinned single crystals of underdoped Fe arsenide superconductors in the "122" family of compounds.