铁硒基超导体的高压研究进展

FeSe及其衍生化合物因表现出奇特的正常态和超导态性质,成为近年来铁基超导领域的研究热点,其中高压技术在揭示FeSe中的竞争电子序和调控高温超导方面发挥了重要作用.本文概述了利用六面砧装置对FeSe基超导体的高压研究进展,主要内容包括:(1)通过建立FeSe的完整温度-压力相图,观察到圆拱形的反铁磁相界并详细揭示了电子向列序、长程反铁磁序和超导相之间的竞争关系,结合高压下的霍尔效应测试进一步表明反铁磁临界涨落对实现高温超导具有重要作用;(2)在多个插层FeSe高温超导体中,普遍发现高压会首先抑制超导I相,然后在临界压力之上诱导出高温超导Ⅱ相,呈现出双拱形超导相图,而且最高临界温度突破50 K;(3)结合高压X射线衍射和霍尔效应测试,指出超导Ⅱ相的出现和伴随的载流子浓度提高很可能源于压力诱导的费米面重构.

Pressure effects on the FeSe-based superconductors

Among the iron-based superconductors,Fe Se and its derived materials have attracted much research interest recently due to its unusual normal-and superconducting-state properties.High-pressure techniques play an important role in unveiling the competing electronic orders and tuning the high-Tcsuperconductivity of Fe Se.In this article,we review the recent progress on the pressure effects of Fe Se-based superconducting materials by using the cubic anvil cell apparatus that can maintain an excellent hydrostatic pressure condition up to 15 GPa.For the bulk Fe Se,we construct a comprehensive temperature-pressure phase diagram,which uncovers a dome-shaped antiferromagnetic phase boundary and reveals the detailed competing relationships between the nematicity,antiferromagnetism,and superconductivity.Our high-pressure Hall results further indicate that the critical antiferromagnetic fluctuations play an important role for achieving the highTcsuperconductivity in Fe Se under high pressure.For the intercalated Fe Se-based high-Tcsuperconductors,we find that the application of high pressure first suppresses the superconducting phase SC-I and then induces a second high-Tc superconducting phase SC-II above a critical pressure Pcwith the optimal Tcover 50 K,resulting in a double-dome shaped phase diagram.In addition,the reemergence of SC-II phase under pressure is found to be accompanied by a concurrent enhancement of electron carrier density.Without structural transition below 10 GPa,the observed SC-II with enhanced carrier density should be ascribed to an electronic origin presumably associated with pressure-induced Fermi surface reconstruction.