Thermoelectric signature of the nematic phase in iron-based superconductor

TL;DR

This paper investigates the thermoelectric signatures of nematic electronic order in iron-based superconductors, revealing broken rotational symmetry as a hallmark of nematicity that persists well above magnetic and structural transition temperatures.

Contribution

It introduces a universal method using Nernst effect anisotropy to detect nematic order in superconductors, applicable across different materials.

Findings

Nernst effect anisotropy indicates nematic order in Ca(Fe1-xCox)2As2

Broken rotational symmetry observed above magnetic transition

Method applicable to other superconductors like Ba(Fe1-xCox)2As2 and YBa2Cu3Oy

Abstract

Studies of the copper-based superconductors demonstrate how their phase diagram becomes more complex as experimental probes improve, able to distinguish among subtly different electronic phases. One of those phases, nematicity, has become the matter of great interest also in the iron-based superconductors, where it is detected deep in the tetragonal state. Here we present the evolution of the in-plane Nernst effect anisotropy in the strain detwinned Ca(Fe1-xCox)2As2 single crystals, whose behaviour can be explained within the approach developed to describe the nematic order parameter in liquid crystals [1,2]. Furthermore, the employed method turns out to be universally applicable to data from other superconductors: Ba(Fe1-xCox)2As2 [3] as well as YBa2Cu3Oy [4]. We conclude the observed broken rotational symmetry of the electronic system is a consequence of the emerging thermodynamic electronic nematic order at a temperature much higher than onset of the magnetic and structural transitions.