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Stronger quantum fluctuation with larger spins: Emergent magnetism in the pressurized high-temperature superconductor FeSe

Yuting Tan (譚宇婷), Tianyu Zhang, Tao Zou, A. M. dos Santos, Jin Hu, Dao-Xin Yao (姚道新), Z. Q. Mao, Xianglin Ke, Wei Ku (顧威)

DOI 10.1103/PhysRevResearch.4.033115 · Physical Review Research

T1

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Abstract

A counterintuitive enhancement of quantum fluctuation with larger spins, together with a few physical phenomena, is discovered in studying the recently observed emergent magnetism in high-temperature superconductor FeSe under pressure. Starting with an experimental crystalline structure from our high-pressure x-ray refinement, we theoretically analyze the stability of the magnetically ordered state with a realistic spin-fermion model. We find, surprisingly, that in comparison with magnetically ordered Fe pnictides, the larger spins in FeSe suffer even stronger long-range quantum fluctuations that diminish their ordering at ambient pressure. This fail-to-order quantum spin-liquid state then develops into an ordered state above 1 GPa due to weakened fluctuation accompanying the reduction of anion height and carrier density. The ordering further benefits from the ferro-orbital order and shows the observed enhancement around 1 GPa. We further clarify the controversial nature of magnetism and its interplay with nematicity in FeSe in the same unified picture for all Fe-based superconductors. In addition, the versatile itinerant carriers produce interesting correlated metal behavior in a large region of phase space. Our paper establishes a generic exotic paradigm of stronger quantum fluctuation with larger spins that complements the standard knowledge of insulating magnetism.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
FeSe

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Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

100Pressure not reportedunknown
K0.8Fe1.6Se2

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Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

—Pressure not reportedunknown

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