Superconductivity in undoped BaFe ₂ As ₂ by tetrahedral geometry design

Abstract

Fe-based superconductors exhibit a diverse interplay between charge, orbital, and magnetic ordering. Variations in atomic geometry affect electron hopping between Fe atoms and the Fermi surface topology, influencing magnetic frustration and the pairing strength through changes of orbital overlap and occupancies. Here, we experimentally demonstrate a systematic approach to realize superconductivity without chemical doping in BaFe2As2, employing geometric design within an epitaxial heterostructure. We control both tetragonality and orthorhombicity in BaFe2As2 through superlattice engineering, which we experimentally find to induce superconductivity when the As−Fe−As bond angle approaches that in a regular tetrahedron. This approach to superlattice design could lead to insights into low-dimensional superconductivity in Fe-based superconductors.

Theoretical Investigation of the Interplay of Superconductivity and Magnetism in Ba1−xKxFe2As2 Superconductor in a Two-Band Model by Using the Bogoliubov Transformation Formalism

“…The addition of a chemical dopant and/or the application of pressure on BaFe 2 As 2 results in the eradication of the SDW and, therefore, in the reduction of magnetic order. Superconductivity is observed when the magnetic order is sufficiently weak; thus, superconductivity and weak magnetic order can still coexist [37,38,40]. The exact mechanism for the emergence of superconductivity is, however, still unknown.…”

Spin-charge-lattice couplings and Co doping effect in Ba(Fe 1 − x He, Yang, Lu et al. 2024Supercond. Sci. Technol.0000View full textAdd to dashboardCite

“…Previous studies have shown that the superconductivities of Ba122 superconductors are affected by various factors. A number of experiments found that the superconducting T c 's are influenced by the geometrical structures [29][30][31], such as the As height with respect to the Fe-Fe plane [32,33] and the Fe-As-Fe angles [34][35][36]. It has also been reported that the magnetism plays a vital role in the superconductivity of Ba122 system [4,[37][38][39].…”

Raman phonon anomalies in Sr(Fe1–x Co x )2As2

“…Superconductivity arises from suppressing the magnetic order and structural phase transition upon doping with electrons or holes. [10] More recently, superconductivity is induced in BaFe 2 As 2 compound without doping or even applying hydrostatic pressure, [11] providing a deeper insight into the interplay between magnetic/structural and superconducting transition. It is clear that magnetic order and superconducting transition are mutually exclusive, however charge nematicity, SDW and structural transition emerge in almost the same region of the phase diagram, resulting in the ambiguity of these orders at transition points.…”