Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba, 277-8561, Japan.
Synchrotron Radiation Research Center, National Institutes for Quantum and Radiological Science and Technology, Sayo, Hyogo, 679-5148, Japan.
Nat Commun. 2017 Oct 26;8(1):1143. doi: 10.1038/s41467-017-01277-x.
A fundamental issue concerning iron-based superconductivity is the roles of electronic nematicity and magnetism in realising high transition temperature (T ). To address this issue, FeSe is a key material, as it exhibits a unique pressure phase diagram involving non-magnetic nematic and pressure-induced antiferromagnetic ordered phases. However, as these two phases in FeSe have considerable overlap, how each order affects superconductivity remains perplexing. Here we construct the three-dimensional electronic phase diagram, temperature (T) against pressure (P) and isovalent S-substitution (x), for FeSe S . By simultaneously tuning chemical and physical pressures, against which the chalcogen height shows a contrasting variation, we achieve a complete separation of nematic and antiferromagnetic phases. In between, an extended non-magnetic tetragonal phase emerges, where T shows a striking enhancement. The completed phase diagram uncovers that high-T superconductivity lies near both ends of the dome-shaped antiferromagnetic phase, whereas T remains low near the nematic critical point.
铁基超导电性的一个基本问题是电子向列性和磁性在实现高温超导（Tc）方面的作用。为了解决这个问题，FeSe 是一种关键材料，因为它表现出独特的压力相图，涉及非磁性向列相和压力诱导的反铁磁有序相。然而，由于 FeSe 中的这两个相有相当大的重叠，每个相如何影响超导性仍然令人困惑。在这里，我们构建了 FeSeS 的三维电子相图，即温度（T）对压力（P）和等价 S 取代（x）。通过同时调节化学压力和物理压力，针对硫族元素高度的对比变化，我们实现了向列相和反铁磁相的完全分离。在两者之间，出现了一个扩展的非磁性四方相，其中 Tc 表现出显著的增强。完整的相图揭示了高温超导性位于穹顶形反铁磁相的两端附近，而在向列临界点附近 Tc 仍然较低。
