超导体研究，特别是探索非常规超导体和高温超导体以及非常规超导理论研究，一直是凝聚态物理的一个重要前沿方向。虽然BCS理论成功地解释了常规超导体的微观机制，但对于之后发现的铜基和铁基等非常规高温超导体来说BCS理论就不能很好适用。虽然人们对非常规超导体诱导配对的原因有部分的认识如：量子涨落、磁性涨落等，但科学家一直以来也没有找到解释非常规超导的统一理论，其原因在于超导现象本身就是电子集体激发的多体现象，再加上非常规超导中还有磁性涨落等非电声子模式的出现，这些纷繁复杂的现象使得描述非常规超导理论变得异常困难，所以探索新超导体对于建立非常规超导理论以及超导体的未来应用都起着至关重要的作用。本论文的工作主要是总结我在一些超导体探索规律的基础上发现的五种类型的超导体。 本论文第一章分为两个小节，第一小节首先是从实验方面介绍了超导的基本现象以及一些特征物理量，之后再列举几个相对成功的唯象理论如伦敦方程，金兹堡朗道方程等，以及BCS超导微观理论。我们比较了这些理论的特点和适用范围，以及从BCS理论得到的一些计算结果。第二小节是关于历史上超导体探索的内容，在这个小节中，先回顾了超导体探索的历史和意义，然后列举了人们在探索超导体中总结出来的几个经验规律：1.Matthias Rules 2.能带交叠效应 3.量子临界效应 4.基本超导单元结构类比法。这些都是人们总结的宝贵经验，非常值得借鉴和学习。最后介绍最近科学家们提出的两个预言超导体的唯象模型：一是耦合强度比较大的σ能带金属化模型，二是从配位环境和电子填充出发的唯象模型。 第二章主要是介绍实验中经常使用的物性测量原理。包括：XRD测量基本原理以及实验方法，电阻率，比热测量以及磁化率测量的基本原理和仪器的构造。 第三章主要内容是总结我们发现的五类新超导体以及其发现过程： (1)我们在国际上首先合成出第一个CrAs单晶，并且利用金刚石对顶砧和静水压技术对其测量了压力下的低温电输运性质，压力下的CrAs在磁性相变抑制后会出现超导性质。CrAs在265K附近存在一级反铁磁结构相变，其相变对压力非常敏感：在比较低的压力下就可以将其抑制；大约在0.3GPa时，压力就可以将相变部分压制，并且在低温下开始出现超导；大约在0.8GPa时，磁性相变被完全压制，超导转变在1.8K附近陡变，之后随着压力增加超导转变温度又慢慢下降，最后完全消失。在最佳压力点时交流磁化率显示样品的超导抗磁体积因子有90％，这说明样品是体超导特性。CrAs是第一个Cr化合物中的超导体，多个实验测量结果表明CrAs是非常规超导体。 (2)我们成功生长出MnAs和MnP的高质量样品，并对这个两个晶体都做了高压低温测量。我们发现MnP在高压下会出现超导性质。MnP与CrAs都属于B8₁正交结构，这个结构存在ZigZag金属链。MnP具有290K的铁磁相变和53K的双螺旋磁性相变。高温的铁磁相变会随压力增加而减小，低温的双螺旋磁性相变在3GPa以内会随压力增加而减小，而这个相变被压制后，又重新出现一个新的反铁磁有序相变，这个新的反铁磁相变温度会随压力增加而升高，最后和高温的铁磁相合在一起后变成一个相变，而它大约在8GPa时会被完全抑制，这时超导出现在1K附近。在超导相图中，超导相的区间非常狭窄，大约只有1GPa的宽度。加压下的MnP也是Mn基化合物的第一个超导体。因其临近磁有序， MnP可能也是非常规超导体。 (3)我们在Cr的三元立方结构化合物Pr₃Cr₁₀N₁₁中发现有超导电性。 Pr₃Cr₁₀N₁₁是已知的物质，但是从来没有人研究过其物理性质，我们在常压下发现其在5.5K就可以超导。Pr₃Cr₁₀N₁₁的上临界场高达12.6T，高于样品的泡利极限临界磁场9.6T。Pr₃Cr₁₀N₁₁是第一个Cr的氮化物超导体。 (4)我们根据α能带金属化的概念，成功地在Sc₃C₄中掺入B并且诱导出超导。Sc₃C₄是四方晶系的材料，其中包含双碳链和三碳链。B的掺入导致了Sc₃C₄中的σ能带或者π键靠近费米面，从而在费米能级处增加了能态密度DOS，这有利于超导的出现。Sc₃C₄掺杂10％的B后，其超导临界温度在8K。这也是在理论的帮助和指导下完成的一次的超导探索。 (5)我们成功合成了第一个WP单晶，并且在0.8K发现其超导性质，这也是MnP结构材料中第一个常压的磷化物超导体。 关键词：非常规超导电性，Cr基超导体，Mn基超导体，强关联电子体系

 The study of superconductivity is one of main fields in the condensed matter physics, especially in finding the unconventional or high Tc superconductors and understanding of their superconducting mechanism. BCS theory has described the microcosmic mechanism of the superconductivity successfully but failed for Cu based and Fe based superconductors. Physicists have a rough mechanism of the origin about unconventional superconductivity, such as: quantum fluctuation, magnetic fluctuation and quantum critical point (QCP) , however, finding a final superconducting mechanism is a tough work for physicists. Superconductivity is a many-body excited phenomenon, additionally the magnetic fluctuation existing in the unconventional superconductity, so the situations become more complex. The research of superconductivity in unconventional superconductors such as heavy-fermions, high transition-temperature cuprates and iron pnictides has been promoting the development of condensed matter physics in recent decades. The superconductivity in these materials usually emerges in the vicinity of long-range antiferromagnetically ordered state. In addition to doping charge carriers, the application of external pressure is an effective way to induce unconventional superconductivity near a magnetic quantum critical point. Our work is to search more new superconductors and help theoretical physicists to establish the final mechanism of unconventional superconductity. The thesis is organized as follows. The first chapter present an overview of the major events related to the phenomenon of superconductivity. We illustrate several mechanisms of superconductivity in various models. We also review four methods related to experience of discovery of superconductors in history. 1.Matthias Rules, 2 Effects of band overlap, 3 Quantum criticality, 4 Analogy with same structral unit of known superconductors. In addition, we present the phenomenological theory to predict high Tc superconductors: 1. Metalation of a band for enhancement of Tc. 2. The gene for high Tc superconductors. The following second chapter describes the experimental details of how to measure the XRD, the resistivity, magnetic susceptibility and specific heat. The third chapter presents our main works for the discovery of 5 new superconductors. (1)The frist one is CrAs. We summarize the basic physical properties of CrAs, and the discovery of superconductivity in the vicinity of double helical antiferromagnetic order in CrAs via external pressure. In addition, we summarize several follow-up studies on structural, magnetic and superconducting mechanism. Accompanied with discontinuous changes of lattice parameters, a first-order double helical magnetic transition occurs at about 265 K. This magnetic transition can be suppressed under pressure, and superconductivity is found at a maximum transition temperature of 2K when the helical magnetic transition is completely suppressed at 0.8 GPa. Some experimental evidences suggest an unconventional pairing mechanism for CrAs. The observations of a dramatic enhancement of the effective mass and non-Fermi-liquid behavior near critical pressure in the transport measurements are the characteristics of antiferromagnetic quantum critical point. Critical spin fluctuations play an important role in understanding the superconductivity of CrAs. The present finding opens a new way for searching novel unconventional superconductors in the Cr and other transition metal-based systems. (2)The second one is MnP. We report the discovery of superconductivity on the border of magnetic order in the helimagnet MnP via the application of high pressure. Superconductivity with T〓 ≈ 1K emerges and exists merely near the critical pressure Pc ≈ 8 GPa, where the long-range magnetic order just vanishes. The present finding makes MnP the first Mn-based superconductor. The close proximity of superconductivity to a magnetic instability suggests an unconventional pairing mechanism. Moreover, the detailed analysis of the normal-state transport properties has proved non-Fermi-liquid behavior and the dramatic enhancement of the quasiparticle effective mass near Pc associated with the magnetic quantum fluctuations. (3)The ternary rare earth chromium nitrides Pr₃Cr₁₀N₁₁ is contaminated by a small amount of Cr₂N. Superconductivity is found at about 5.2K and H〓 is 12.6T beyond the Pauli limit. Pr₃Cr₁₀N₁₁ is the first superconductor in chromium nitrides compounds. (4)The cystal structure of Sc₃C₄ is a Carbide with C3 unit. It crystallizes in a tetragonal structure with space group P4/mnc. Sc₃C₄ shows a Pauli paramagnetism and a metallic conduction at low temperatures. If we doped with 10% B into the C site, superconductivity transition at about 8K is observed. This may be induced by raising the σ or π band above the Fermi level. (5)We discovered the superconductivity in WP near 0.8K, WP belongs to the B8₁ structure, which is same structure with CrAs and MnP. Kay words: Unconventional superconductivity; Cr-based superconductors; Mn-based superconductors; Quantum criticality; Strongly-correlated electron systems