准一维过渡金属砷化物超导体的探索和物性研究

Exploration of new superconductors has always been one of the most attractive topics in condensed matter physics. In recent years we have always been focusing on the exploration of new superconductors. In 2015 we reported the discovery of the quasi-one-dimensional chromium pnictide superconductors A2Cr3As3(A = K, Rb, Cs). Theories and experimental results reveal their peculiar properties, which mostly point to unconventional superconductivity. In this project, we propose to further extend our research field to other transition metal arsenide containing quasi-one-dimensional structure basing on our previous work. On the one hand, we try to find new superconductors in this kind of compounds and study their physical properties through a combination of electrical transport, magnetic susceptibility and heat-capacity measurements. On the other hand, we plan to effectively adjust the parameters such as band structure, carrier concentration by chemical doping into new superconductors, so that we can look for the experimental evidences for the superconducting order parameters and clarify the different types of impurity effect on superconductors. Meanwhile, the possibility of enhancing the critical temperature of this kind of superconductors can be explored.

新型超导材料的探索一直是凝聚态物理中重要的研究内容。近年来我们一直致力于新型超导材料的探索，并在2015年报道了首个常压上超导的准一维铬砷化合物超导体A2Cr3As3(A = K, Rb, Cs)，目前的理论和实验结果大都表明他们具有非常规超导电性。本项目拟在前期工作的基础上，将研究领域进一步扩展到其他具有准一维结构的过渡金属砷化物，一方面探索这类化合物中存在的新型超导体，通过电输运，磁性测量和比热测量研究其物性；另一方面，对新型超导体进行化学掺杂，来有效调节能带结构、载流子浓度等参数，寻找确定超导序参量对称性的实验证据和影响超导电性的各种杂质效应；同时探索在此类超导体中进一步提高转变温度的可能性。

准一维铬基超导体A2Cr3As3(A=K,Rb,Cs)的发现引起了广泛的关注，因为它们有可能是自旋三重态的非常规超导体。室温下利用无水乙醇，可以把A2Cr3As3脱去一半的A+离子，得到同样具有准一维铬砷链的化合物ACr3As3，之前报道ACr3As3多晶不超导，基态是自旋玻璃态，但单晶在5K下会发生超导转变。我们利用老化和退火处理KCr3As3，发现母体ACr3As3是不超导的，基态是自旋玻璃态，超导的出现是因为由于老化和退火的处理，氢进到了铬砷链里面。利用元素替换，我们在A-Ni-As上发现了一个新的超导相，具体的结构和组分还有待进一步研究。