Field-induced incipient spin-density phase stabilized inside the nematic phase of FeSe$_{1-x}$S$_x$
Year: 2026
Type: preprint
Abstract: Spin-density wave (SDW) order and superconductivity frequently compete and coexist in unconventional superconductors, where spin fluctuations often mediate superconducting pairing. In iron-chalcogenide superconductors, FeSe$_{1-x}$S$_x$, SDW order has only been detected under applied pressure, while both spin and nematic fluctuations are involved in determining their rich superconducting phase diagrams. Here, we report evidence for an incipient SDW phase, within the nematic state of FeSe$_{1-x}$S$_x$, revealed in magnetic fields up to 68~T. Once superconductivity is quenched, we observe sharp upturns in longitudinal resistivity accompanied by anomalies in tunnel diode oscillator frequency response and torque anisotropy, consistent with a field-induced electronic order. Dominant low-frequency quantum oscillations reveal a small reconstructed Fermi surface, consistent with a field-induced SDW order. Direct experimental comparisons with a pressure-tuned nematic, analogue, FeSe$_{0.96}$S$_{0.04}$, demonstrate that SDW phases are stabilized within the nematic phase of FeSe$_{1-x}$S$_x$ via both chemical substitution and applied pressure. These findings reveal that by weakening nematicity, the SDW orders are stabilised, which promotes the dominant superconducting pairing mechanism in iron chalcogenides.
Source: arXiv (Cornell University)
Institutions: University of Oxford, Centre National de la Recherche Scientifique, Laboratoire National des Champs Magnétiques Intenses, Florida State University, National High Magnetic Field Laboratory, Karlsruhe Institute of Technology, Institut National des Sciences Appliquées de Toulouse, Université Grenoble Alpes
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: G169999952, G2074034901, DTP 2224 University of Oxford, G3180218165, DTP 2016-2017 University of Oxford, Membership of the UK to the European Magnetic Field Laboratory, Emergent phenomena in novel correlated materials, Improving the sustainability of the European Magnetic Field Laboratory, DTP 2018-19 University of Oxford, G7953190121
OpenAlex ID: W7214146575