Liu Hongtao, Xue Yunzhou
College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518052, P. R. China.
Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, P. R. China.
Adv Mater. 2021 Apr;33(17):e2008456. doi: 10.1002/adma.202008456. Epub 2021 Mar 23.
Layered iron chalcogenides (FeX, X = S, Se, Te) provide excellent platforms to study intertwined phase transitions, superconductivity, and magnetism. However, layered iron dichalcogenides (FeX , X = S, Se, Te) are rarely reported and their intrinsic properties are still unknown. Here, phase-pure layered iron diselenide (FeSe ) nanocrystals are epitaxially grown on mica by the sublimed-salt-assisted chemical vapor deposition method at atmospheric pressure. The layered atomic structure of FeSe is confirmed by X-ray diffraction and atomic-resolution scanning transmission electron microscopy. Electrical transport shows that the layered FeSe is a metal with high conductivity and a phase transition at ≈11 K. The phase transition manifests itself as a kink in the temperature-dependent resistivity, as well as anomalous magnetoresistance (MR) appearing around the phase-transition temperature. The MR changes from negative to positive, accompanied by large hysteresis near the phase-transition temperature upon cooling. The negative MR and hysteresis might originate from magnetic field suppression scattering of spin fluctuations and competition of magnetic interactions induced by the phase transition, respectively. Layered iron dichalcogenide will be potential candidate to explore novel quantum phenomena and other applications.
层状铁硫族化合物（FeX，X = S、Se、Te）为研究相互交织的相变、超导性和磁性提供了绝佳的平台。然而，层状二硫族化铁（FeX₂，X = S、Se、Te）的报道却很少，其本征性质仍不为人知。在此，通过常压下升华盐辅助化学气相沉积法，在云母上外延生长出相纯的层状二硒化铁（FeSe₂）纳米晶体。通过X射线衍射和原子分辨率扫描透射电子显微镜确认了FeSe₂的层状原子结构。电输运表明，层状FeSe₂是一种具有高电导率的金属，在约11 K时发生相变。该相变表现为与温度相关的电阻率出现扭折，以及在相变温度附近出现反常磁电阻（MR）。MR从负变为正，冷却时在相变温度附近伴有大的磁滞现象。负MR和磁滞现象可能分别源于自旋涨落的磁场抑制散射和相变诱导的磁相互作用竞争。层状二硫族化铁将是探索新型量子现象及其他应用的潜在候选材料。
