Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained BaFe2As2

Mingquan He,Felix Ahn,Jörg Schmalian,Ilya Eremin,Peter Adelmann,Frédéric Hardy,Liran Wang,Thomas Wolf,Christoph Meingast

doi:10.1038/s41467-017-00712-3

Abstract

High-temperature superconductivity in the Fe-based materials emerges when the antiferromagnetism of the parent compounds is suppressed by either doping or pressure. Closely connected to the antiferromagnetic state are entangled orbital, lattice, and nematic degrees of freedom, and one of the major goals in this field has been to determine the hierarchy of these interactions. Here we present the direct measurements and the calculations of the in-plane uniform magnetic susceptibility anisotropy of BaFe2As2, which help in determining the above hierarchy. The magnetization measurements are made possible by utilizing a simple method for applying a large symmetry-breaking strain, based on differential thermal expansion. In strong contrast to the large resistivity anisotropy above the antiferromagnetic transition at TN, the anisotropy of the in-plane magnetic susceptibility develops largely below TN. Our results imply that lattice and orbital degrees of freedom play a subdominant role in these materials.

Highlights

High-temperature superconductivity in the Fe-based materials emerges when the antiferromagnetism of the parent compounds is suppressed by either doping or pressure
Many optimally doped Fe-based materials appear to be close to a putative nematic quantum critical point[28], and recent theoretical works suggest that electronic nematic fluctuations may provide a boost to superconductivity in various channels[37]
Samples were glued onto a glass-fiberreinforced plastic (GFRP) substrate with the crystal’s tetragonal

Summary

Introduction

High-temperature superconductivity in the Fe-based materials emerges when the antiferromagnetism of the parent compounds is suppressed by either doping or pressure. TN, which is driving has raised the question of these transitions[8,9,10,11], or whether whether orbital degrees of freedom need to be considered[12,13,14,15] This issue is pressing for FeSe, which has no long-range magnetic order down to the lowest temperature at ambient pressure but exhibits a similar orthorhombic distortion as the other Fe-based materials[16,17,18]. This non-magnetic and orthorhombic phase has been coined “electronic nematic”[10, 19]. We study the interplay between lattice, orbital, magnetic, and nematic degrees of freedom in the parent compound

Methods

Results

Conclusion