Cr基和Mn基新超导体探索和及非常规超导电性研究

Recently，the applicant of this project and his collaborators discovered superconductivity near a quantum critical point in CrAs and MnP under pressure. These are the first superconductors among the Cr- and Mn-based compounds. The discovery made that the superconductivity could be observed in all the 3d element-based compounds. In this project, we will carry out a systematically study on the unconvebtional superconductivity and the quantum criticality and in Cr- and Mn- based compounds. By control the different parameters including temperature, .magnetic field, electric field, pressure, as well as elements substitutions, we will study the thermodynamic properties, transport properties, electronic structure, and low-lying spin and charge excitations in the systems. Our aim is to understand the physical origin of quantum phase transition and non-Fermi liquid behaviors, to uncover the relationship between quantum criticality and unconventional superconductivity, and to search for novel unconventional superconductors in the Cr- and Mn- based materials.

最近，项目申请人及合作者在CrAs和MnP中通过加压在量子临界点附近发现超导，这是Cr基和Mn基化合物的第一个超导体，其发现使得所有3d过渡族元素均具有超导的化合物。本项目将在此基础上开展Cr基和Mn基化合物的量子临界性和非常规超导电性研究和新超导体探索。在Cr基和Mn基化合物中，通过调控多个自由度（温度，磁场，电场，压力，元素置换等），对其热力学性质、输运性质、电子结构、自旋和电荷激发进行多方面的深入研究，理解这些材料中量子相变和非费米液体行为的起源，揭示量子临界行为和非常规超导电性的关系。在Cr基和Mn基材料中探索新的超导体、乃至高温超导体。

本项目在Cr基和Mn基及相关材料中探索新的超导体，同时对其超导电性进行研究。发现第一个Tc为5.3K的Cr基氮化物超导体Pr3Cr11N10和4.6K的La3Cr11N10，并且发现新超导体具有非常规超导体特征：如上临界场非常大，超出Pauli极限，实验测得的态密度是能带计算的10倍，表明电子强关联，uSR实验发现在Tc处时间反演对称破缺，表明其可能是p-wave超导。发现具有MnP结构的5d过渡金属化合物超导体WP，Tc为8K的轻元素超导体Sc-B-C。研究了CrAs压力和P掺杂下的输运、比热和中子散射等实验，发现临界压力下量子临届行为及其和非常规超导的关系。研究了K2Cr3As3的低温和强磁场下的比热，发现其低温下比热随温度以T2 的规律变化，随磁场以H0.5的规律变化，表明其超导能隙函数存在节线。共发表学术论文15篇，培养学生5名。