期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：23
页码：12606-12610
DOI：10.1073/pnas.2000833117
出版社：The National Academy of Sciences of the United States of America
摘要：We studied the electrical transport of Fe 4 δ Se 5 single-crystal nanowires exhibiting √5 × √5 Fe-vacancy order and mixed valence of Fe. Fe 4 δ Se 5 compound has been identified as the parent phase of FeSe superconductor. A first-order metal-insulator (MI) transition of transition temperature T MI ∼ 28 K is observed at zero magnetic fields ( B ). Colossal positive magnetoresistance emerges, resulting from the magnetic field-dependent MI transition. T MI demonstrates anisotropic magnetic field dependence with the preferred orientation along the c axis. At temperature T < ∼17 K, the state of near-magnetic field-independent resistance, which is due to spin polarized even at zero fields, preserves under magnetic fields up to B = 9 T. The Arrhenius law shift of the transition on the source-drain frequency dependence reveals that it is a nonoxide compound with the Verwey-like electronic correlation. The observation of the magnetic field-independent magnetoresistance at low temperature suggests it is in a charge-ordered state below T ∼ 17 K. The results of the field orientation measurements indicate that the spin-orbital coupling is crucial in √5 × √5 Fe vacancy-ordered Fe 4 δ Se 5 at low temperatures. Our findings provide valuable information to better understand the orbital nature and the interplay between the MI transition and superconductivity in FeSe-based materials.
关键词：Verwey transition ; Fe-vacancy order ; colossal magnetoresistance
