Anomalous suppression of the orthorhombic distortion in superconducting Ba[Fe(1-x)Cox]2As2

TL;DR

This study uses high-resolution x-ray diffraction to show that superconductivity in Ba[Fe(1-x)Cox]2As2 suppresses orthorhombic lattice distortion, likely through magneto-elastic coupling and nematic order, revealing a strong interplay between structural and electronic phases.

Contribution

It demonstrates the suppression of orthorhombic distortion in superconducting Ba[Fe(1-x)Cox]2As2 and suggests an indirect coupling mechanism involving nematic order.

Findings

Orthorhombic distortion is suppressed in superconducting samples.

Near x=0.063, the structure transitions smoothly to tetragonal.

Coupling between orthorhombicity and superconductivity is mediated by nematic order.

Abstract

High-resolution x-ray diffraction measurements reveal an unusually strong response of the lattice to superconductivity in Ba[Fe(1-x)Cox]2As2. The orthorhombic distortion of the lattice is suppressed and, for Co-doping near x = 0.063, the orthorhombic structure evolves smoothly back to a tetragonal structure. We propose that the coupling between orthorhombicity and superconductivity is indirect and arises due to the magneto-elastic coupling, in the form of emergent nematic order, and the strong competition between magnetism and superconductivity.