低维过渡金属硫属化物超导体的探索和物性研究

The low-dimensional transition metal chalcogenides are a kind of compounds with both low-dimensional structures and correlated electrons, which show complex electronic ground states depending on the different crystalline structures. Among the transition metal dichalcogenides, researchers discovered a series of new superconductors, which not only show the coexistence of different electronic ground states, but also have the quasi-two-dimensional electronic structures similar to that of high-temperature superconductors. However, there is still no definite conclusions about the superconducting mechanisms for this kind of superconductors. The crystalline forms for low-dimensional transition metal chalcogenides containing the elements more than two are more diverse, taking which as the objects to explore and study new superconductors is full of opportunities. We always focus on the exploration of new superconductors and investigation of superconducting mechanisms in recent years, and have found the new superconductor Ta4Pd3Te16. In this project, we propose to further extend our research field to other transition metal chalcogenides containing the elements more than two, based on our previous work. In one aspect, we will explore other new superconductors in this kind of low-dimensional compounds and study its physical properties with full measurements of electro-transport, magnetic and thermal properties. In the other aspect, by element intercalation or chemical doping into the layered chalcogenide superconductors, we plan to effectively mediate the parameters such as band structure, carrier concentration, and quest for the evolving relation of the superconductivity with mediating parameters to summarize up the law. Moreover, efforts will be made to explore the possibility of further enhancing the critical temperature of this kind of superconductors.

低维过渡金属硫属化物是一类兼具结构低维性和关联电子的系列化合物，依其不同构成呈现出丰富多彩的电子基态。在此类二元化合物中，研究人员发现了一系列的超导体，其同时具有多自由度竞争的电子基态和类似于高温超导体的准二维电子结构，但超导机理仍不明确。三元以及三元以上的低维过渡金属硫属化物的构成更加丰富，以其为对象探索和研究新型超导体充满机遇。近年来我们一直致力于新型超导体的探索和机理研究，并在三元过渡金属硫属化物中发现了新的超导体Ta4Pd3Te16。本项目拟在前期的工作基础上，将研究范围扩展到其他的三元以及三元以上的低维过渡金属硫属化物，一方面探索这类化合物中可能存在的新型超导体，通过磁性、输运性质和比热测量研究其物理性质；另一方面对已发现的低维硫属化物超导体通过元素插层或化学掺杂来有效调节能带结构、载流子浓度等参数，寻找超导随调控参数的演化关系并总结规律，同时探索进一步提高转变温度的可能性。

低维过渡金属硫属化物，是一类通常具有结构低维性和强关联电子的系列化合物，依其不同构成呈现出丰富多彩的电子基态，如非常规超导电性，电荷密度波等。本项目以此类化合物为研究对象，探索新型超导体和具有奇异量子基态的材料。利用极端条件下（强磁场、极低温等）的输运、热力学性质测量等多种实验手段，重点研究了如下几个重要的科学问题：（1）我们发现了一种具有准一维结构特征的超导转变温度为1K的新型碲化物超导体Ta3Pd3Te14，通过输运，热力学性质的测量，对其物性和可能的超导配对机制进行了研究；（2）通过测量超导体Ta4Pd3Te16的正常态磁阻、霍尔和热电势，对其正常态性质进行了详细的物理性质研究，为揭示Ta4Pd3Te16超导机理提供更多实验依据；（3）我们发现一种新低维过渡金属碲化物TaPdTe5；（4）通过低温比热等测量，研究具有较强自旋-轨道耦合的超导体La7Ir3的低能电子激发，探索其超导配对的机理；（5）发现了一种具有拓扑电子结构的碲化物NiTe2,研究了其Dirac电子对输运、热力学性质的影响；（6）发现了一种铁基铁磁超导体Eu(Fe0.91Rh0.09)2As2,在对其物理性质进行研究的同时，我们通过细致的磁测量，我们揭示了铁磁和超导在此化合物中共存的方式。