Divergent nematic susceptibility in an iron arsenide superconductor

TL;DR

This paper demonstrates how measuring divergent nematic susceptibility in an iron arsenide superconductor can distinguish electronic nematic phase transitions from structural distortions and reveals an electronic nematic quantum critical point at optimal doping.

Contribution

It introduces a method to identify electronic nematic phase transitions via susceptibility measurements, clarifying the nature of the transition in iron-based superconductors.

Findings

Divergent nematic susceptibility indicates an electronic nematic phase transition.

Electronic nematic quantum phase transition occurs at optimal superconductivity.

Measurement distinguishes electronic nematic order from structural distortions.

Abstract

Within the Landau paradigm of continuous phase transitions, ordered states of matter are characterized by a broken symmetry. Although the broken symmetry is usually evident, determining the driving force behind the phase transition is often a more subtle matter due to coupling between otherwise distinct order parameters. In this paper we show how measurement of the divergent nematic susceptibility of an iron pnictide superconductor unambiguously distinguishes an electronic nematic phase transition from a simple ferroelastic distortion. These measurements also reveal an electronic nematic quantum phase transition at the composition with optimal superconducting transition temperature.