Emergent high-spin state above 7 GPa in superconducting FeSe

Abstract

The local electronic and magnetic properties of superconducting FeSe have been investigated by K$\beta$ x-ray emission (XES) and simultaneous x-ray absorption spectroscopy (XAS) at the Fe K-edge at high pressure and low temperature. Our results indicate a sluggish decrease of the local Fe spin moment under pressure up to 7~GPa, in line with previous reports, followed by a sudden increase at higher pressure which has been hitherto unobserved. The magnetic surge is preceded by an abrupt change of the Fe local structure as observed by the decrease of the XAS pre-edge region intensity and corroborated by ab-initio simulations. This pressure corresponds to a structural transition, previously detected by x-ray diffraction, from the $Cmma$ form to the denser $Pbnm$ form with octahedral coordination of iron. Finally, the near-edge region of the XAS spectra shows a change before this transition at 5~GPa, corresponding well with the onset pressure of the previously observed enhancement of $T_c$. Our results emphasize the delicate interplay between structural, magnetic, and superconducting properties in FeSe under pressure.

4 pages

References in corpus (14)

• Superconductivity at 36 K in beta-Fe1.01Se with the compression of the interlayer separation under pressure
• Orbital-driven nematicity in FeSe
• Crystal structure of the new FeSe1-x superconductor
• Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe
• Theoretical evidence for strong correlations and incoherent metallic state in FeSe
• The Galaxies Beamline at SOLEIL Synchrotron: Inelastic X-ray Scattering and Photoelectron Spectroscopy in the Hard X-ray Range
• Strong cooperative coupling of pressure-induced magnetic order and nematicity in FeSe
• High temperature superconductivity (Tc onset at 34K) in the high pressure orthorhombic phase of FeSe
• Charge induced nematicity in FeSe
• Pressure Induced Stripe-order Antiferromagnetism and First-order Phase Transition in FeSe
• A study of electronic structure of FeSe${}_{1-x}$Te${}_x$ chalcogenides by Fe and Se K-edge x-ray absorption near edge structure measurements
• Magnetotransport study of the pressure-induced antiferromagnetic phase in FeSe
• Pressure induced magnetic order in FeSe
• Complex biphase nature of the superconducting dome of the FeSe phase diagram

Cited by in corpus (8)

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• Epsilon-iron as a spin-smectic state
• Spontaneous orbital polarization in the nematic phase of FeSe
• Distinct pressure evolution of coupled nematic and magnetic order in FeSe
• Robust block magnetism in the spin ladder compound BaFe${}_2$Se${}_3$ under hydrostatic pressure
• Disappearance and Survival of Superconductivity in FeSe under High Pressure
• Magnetic and structural properties of the iron silicide superconductor LaFeSiH