强关联电子系统超导电性的高压研究

High Pressure Studies on Superconductivity of Strongly Correlated Electron Systems

具有强关联电子特性的凝聚态系统中,电子间的强关联性主导系统的宏观量子特性。这类系统具有电荷、自旋、轨道、晶格及拓扑等多重自由度,这些自由度强烈耦合,产生复杂的多体相互作用,导致系统出现丰富奇异的量子现象,如非常规超导电性、庞磁电阻、金属-绝缘体转变、拓扑量子相变等。其中,非常规超导体的研究于近几十年取得了不少进展,例如发现了铜氧化物高温超导电性和铁基超导体,然而导致非常规超导电性的原因,尤其是对高温超导电性的机理认识目前尚不清楚,非常规超导机理一直是凝聚态物理研究领域中最具挑战性的问题之一。为此,简要介绍了近年来我们通过高压实验手段在重费米子超导体、铜氧化物超导体和铁基超导体这3类主要的非常规超导体研究中取得的进展、发现的新现象以及反映的新物理机理,包括磁性和超导电性的演化关系、价态变化对超导电性的影响、铜氧化物的普适压力相图等,旨在提供非常规超导体在高压研究方面的一些实验新进展,以期为更好地理解非常规超导的微观机理提供压力维度下的一些信息。

The coexistence and interplay between spin,charge,orbital and lattice in electron correlated systems give rise to many interesting quantum phenomena,including unconventional superconductivity,colossal magnetoresistance,metal-insulator transition,topological phase transition,etc.While,as one of the most important issues in condensed matter physics,the mechanism of the unconventional high temperature superconductivity is still unclear up to now.In this paper,we report some new phenomena/physics obtained from our high pressure studies on three typically unconventional superconductors—heavy fermion superconductor,cuprate high temperature superconductor and iron-based superconductor,which include the correlation between magnetism and superconductivity,the influence of valence change on superconductivity,the discovery of superconductivity reemerging,the bi-critical points,and the universal transition from superconducting to insulating-like states,etc.These high-pressure experimental results on the unconventional superconductors are expected to provide useful information for a better understanding on the unconventional superconducting mechanism.