Study on correlation between magnetism and superconductivity in f-electron systems

我们已经研究了几个典型的重费米子化合物，包括Ce和U基磁性超导体和Sm基价态涨落材料，在热力学，磁性和输运测量与中子散射技术。我们得到了以下结果。1.揭示了UPd_2Al_3和UNi_2Al_3的自旋动力学，并成功探测到了它们的de Haas-van Alphen效应信号.我们得到了URu_2Si_2的压力-温度相图，该相图显示出隐藏有序态和超导性共存，并揭示了一条一级相线（称为Sato线），该相线分隔隐藏有序态和反铁磁有序态。我们还指出，超导态被压力下出现的反铁磁性所破坏。我们观察到UGe_2的超导转变温度在压力下呈现双峰结构。在两个临界压力附近的双峰结构是否存在， ...更多信息 这意味着存在两个不同的超导区.我们发现CeRhIn_5在常压下也有超导电性。从超导转变温度和Neel温度对压力的依赖关系出发，借助理论模型，我们提出了费米面上一个态的超导性和反铁磁性竞争共存.我们构造了典型的混合价化合物SmS的压力-温度相图，并揭示了在所谓的黄金相中存在赝能隙。这清楚地解决了长期存在的分歧是否金SmS是一种金属或半导体。我们构建了一个装置，在压力下的膨胀和直流磁化实验。我们还研制了一台利用木炭泵的_3He制冷机，揭示了重费米子材料的某些方面，解决了重费米子物理领域中的一些基本问题，但其基础物理问题仍有待解决。少

We have studied several typical heavy fermion compounds, including Ce-and U-based magnetic superconductors and a Sm-based valence fluctuating material, in terms of thermodynamic, magnetic, and transport measurements together with the neutron scattering technique. We obtained the following results.1. We revealed the spin dynamics of UPd_2Al_3 and UNi_2Al_3, and succeeded in detecting de Haas-van Alphen effect signals for them.2. We obtained a pressure-temperature phase diagram of URu_2Si_2 that exhibits the coexistence of hidden order and superconductivity, and revealed a first order phase line (called Sato line) that separates the hidden and antiferromagnetic ordered states. We also indicated that the superconducting state is destroyed by the antiferromagnetism emerging under pressure.3. We observed that the superconducting transition temperature of UGe_2 exhibits a twin peak structure under pressure. It remains an open question whether the twin peak structure at around two critical pr … More essures implies the existence of two different superconducting regions.4. We found that the superconductivity appears even at ambient pressure for CeRhIn_5. From the pressure dependence of the superconducting transition temperature and Neel temperature, with the help of a theoretical model, we suggested that the superconductivity and antiferromagnetism competitively coexists for a state on the Fermi surface.5. We constructed a pressure-temperature phase diagram of the typical mixed valence compound SmS, and revealed the existence of a pseudogap in the so-called golden phase. This clearly resolves the long-standing discrepancy whether golden SmS is a metal or a semiconductor.We constructed an apparatus for dilatation and dc magnetization experiments under pressure. We also developed a _3He refrigerator using a charcoal pump.As a result, we revealed some aspects of the heavy fermion materials and solved some of fundamental problems in the field of the heavy fermion physics, although the underlying physics remains to be resolved. Less