Local atomic configuration control of superconductivity in the undoped pnictide parent compound BaFe2As2

TL;DR

This study demonstrates a method to control superconductivity in BaFe2As2 thin films by manipulating local atomic configurations through structural factors like orthorhombicity and tetragonality, without chemical doping.

Contribution

It introduces a systematic approach to tune local atomic arrangements and superconductivity in BaFe2As2 via substrate-induced strain, avoiding chemical doping.

Findings

Superconductivity can be tuned by controlling orthorhombicity and tetragonality.

Structural phase transition and magnetism are controllable through lattice parameters.

Superconductivity is achievable without chemical doping in thin films.

Abstract

Emergent superconductivity is strongly correlated with the symmetry of local atomic configuration in the parent compounds of iron-based superconductors. While chemical doping or hydrostatic pressure can change the local geometry, these conventional approaches do not provide a clear pathway in tuning the detailed atomic arrangement predictably, due to the parent compounds complicated structural deformation in the presence of the tetragonal-to-orthorhombic phase transition. Here, we demonstrate a systematic approach to manipulate the local structural configurations in BaFe2As2 epitaxial thin films by controlling two independent structural factors orthorhombicity (in-plane anisotropy) and tetragonality (out-of-plane/in-plane balance) from lattice parameters. We tune superconductivity without chemical doping utilizing both structural factors separately, controlling local tetrahedral coordination in designed thin film heterostructures with substrate clamping and bi-axial strain. We further show that this allows quantitative control of both the structural phase transition, associated magnetism, and superconductivity in the parent material BaFe2As2. This approach will advance the development of tunable thin film superconductors in reduced dimension.