Study of the interplay of Magnetism, Structure, and Electronic Properties in the Iron-Based superconductor BaFe2S3 – (Yassine Oubaid / LNCMI / Seminar). – 18/06/2026, 14H

Seminar LNCMI

Yassine Oubaid, Laboratoire de Physique du Solide at Université Paris Saclay

Seminar LNCMI, 18/06/2026, 14H, LNCMI, Toulouse

Abstract
Recently, a family of quasi-one-dimensional Fe-based spin-ladder compounds with the formula BaFe2X3, where X represents a chalcogen (Se or S), has been shown to exhibit superconductivity under pressures exceeding 10 GPa, with critical temperatures of approximately 10 K or 26 K, depending on the chalcogen species [1].

However, the intriguing properties of these compounds extend far beyond superconductivity. At ambient pressure, they behave as Mott insulators and display exotic structural and magnetic phenomena, including multiferroicity near room temperature. As such, these materials encompass key characteristics of strongly correlated quantum systems. Building on extensive investigations of BaFe2Se3, this work presents a comprehensive experimental study of BaFe2S3.

A detailed examination of the structural, magnetic, and electronic properties of BaFe2S3 as a function of temperature and pressure was carried out using a multi-technique approach. This included synchrotron X-ray diffraction, neutron diffraction, inelastic neutron scattering, and synchrotron-based infrared spectroscopy, performed on both powder and single crystals from the same synthesis batch. These experiments enabled the construction of a comprehensive picture of the underlying physics as a function of temperature and pressure. At ambient pressure, our study revealed novel phases featuring new atomic structures and a previously unreported structural transition to a polar structure, demonstrating that BaFe2S3 hosts a combination of exotic tilted stripe magnetic order, multiferroicity, and magnetoelasticity [2, 3].

Under pressure, by combining complementary structural, magnetic, optical, and transport measurements, we obtained a comprehensive picture of the magnetic and atomic evolution of BaFe2S3. Our results provide evidence for an intriguing dichotomy between localized and itinerant Fe 3d electrons, which helps explain both the persistence of magnetic order and the emergence of superconductivity. In particular, we have significantly revised the interpretation of several experimental observations previously reported in the literature, substantially enhancing our understanding of magnetoelastic coupling, electronic gap opening, the insulator-to-metal transition, structural degrees of freedom, and superconductivity.

[1] H. et al. Takahashi. Pressure-induced superconductivity in the iron-based ladder material BaFe2S3. Nature Materials, 14:1008–1012, 2015.

[2] Y.Oubaid et al. New insight on the properties of the superconducting iron spin ladder BaFe2S3. Frontiers of Physics, 21(5):055201, 2026.

[3] Y.Oubaid et al. Ground state of BaFe2S3 from lattice and spin dynamics. Physical Review B, 2026. Accepted.

Lien Zoom : https://univ-grenoble-alpes-fr.zoom.us/j/94228207316?pwd=khTdznxeFy1ZUYkYftQ0QSox6Fz3iK.1