Two superconducting domes in FeS - Fengliang Liu

SEPTEMBER 1, 2017

A team co-led by HPSTAR PhD student Fengliang Liu, investigated the evolution of superconductivity and structure with pressure for the new superconductor FeS (Tc ≈ 4.5 K), a sulfide counterpart of FeSe. They observed two superconducting domes in FeS under compression with 30% enhancement in maximum Tc in the second dome. Their discoveries are published by NPJ Quantum Materials (DOI:10.1038/s41535-017-0050-7).

Iron-based superconductors are of great interest and fundamental importance due to their rich structural and physical properties. Isostructural to the FeSe superconductor, tetragonal FeS has attracted considerable attention due to its many similarities in crystal and electronic structures with FeSe. It provides us a new and simple platform as FeSe to realize high-temperature superconductors and to study the underlying mechanism of iron-based superconductivity.

“It is of fundamental importance to know whether pressure still affects FeS and how pressure tune the superconductivity of FeS, and how this relates to its structural properties at atomic level”, said Fengliang.

So the team applied in-situ high-pressure electrical transport and synchrotron X-ray diffraction (XRD) measurements on tetragonal FeS single crystals to find how pressure affects the physical properties of FeS.

Upon applying pressure, they observed that the Tc in the first superconducting dome continuously decrease with increasing pressure which vanishing superconductivity around 4GPa. The scond superconducting dome emerges from 5.0 GPa and lasts to 22.3 GPa, with an over 30% increasing in Tc (≈6.0 K) from the highest Tc in the first dome.

“The two superconducting domes we observe here in FeS are quite different from that of other iron-based superconductors. For FeS, we thought that the second superconducting dome is from the residual deformed tetragonal phase” explained Fengliang.

Caption: a: The pressure dependence of phase contents around the structure transition, which are obtained through refinements. b: Temperature–pressure phase diagram of FeS. There are apparently two superconducting domes, and the second dome is attributed to the remaining tetragonal phase.

媒体报道：

知社学术圈： http://www.yidianzixun.com/article/0HDjVuz7

自被发现以来，超导一直是科学界研究的重要内容之一，随着科技的进步和发展，超导的研究也越发的多样化，而提高超导转变温度，寻找潜在的室温超导体是科技工作者一直以来梦寐以求的最高理想。近期，北京高压科学研究中心的杨文革研究员小组和上海复旦大学的李世燕教授研究小组携手合作，通过金刚石对顶砧的实验方法模拟地球内部压力对四方FeS超导体的高压输运性质进行了一系列的研究。研究团队发现，四方FeS随压力表现出“超导—超导消失—超导再现—超导消失”的双超导相行为，且新超导相的超导转变温度提高了30%，这一研究成果发表在9月1日的《npj Quantum Materials》上。