Physics of Spin-Triplet Superconductivity

我们第一次确定了一个超导体，它的电子以自旋三重态成对存在。通过对钌酸盐超导体Sr_2RuO_4的广泛研究，我们获得了超导研究中的一些新的关键概念：(1)超导多间隙的测定：我们设计了一种测定每个费米面上超导间隙的方法。对于Sr_2RuO_4，我们基于自旋-三重态对称性和自旋涨落了解了其多隙结构的物理起源。(2)铜对自旋态的确定：通过核磁共振（NMR）确定了三态自旋位于RuO_2平面内，但在弱磁场作用下可以自旋。(3)奇宇称的证实：我们制作了由Sr_2RuO_4和s波超导体AuIn组成的pi结超导量子干涉器件SQUID (Superconducting QUantum Interference Device)，并证明了Sr_2RuO_4的超导波函数的宇称是奇，这是自旋三重态超导的必要条件。(4)超导机制理论框架的构建：基于强相关电子间的库仑排斥，成功构建了超导机制的一般理论框架。通过将其应用于Sr_2RuO_4的详细现实模型，我们可以得出自旋三重态对比其他态更稳定。我们还发现了氧化银铅Ag_5Pb_2O_6的超导性，阐明了（Ca,Sr）_2RuO_4中Mott跃迁和轨道有序的机理，揭示了Sr_3Ru_2O_7中的超磁量子临界现象。我们主办了“自旋-三重态超导与钌酸盐物理”国际研讨会，该领域的大部分活跃研究人员参加了研讨会，其中包括来自国外8个国家的20多名研究人员。

We firmly established for the first time that a superconductor with its electrons paired in a spin-triplet state actually exists. Through extensive investigations focusing on the ruthenate superconductor Sr_2RuO_4,we obtained a number of new key concepts in the study of superconductivity :(1) Determination of the superconducting multi-gaps : We devised a method of determining the superconducting gap on each of the Fermi surface. For Sr_2RuO_4,we understand the physical origin of its multi-gap structure based on the spin-triplet symmetry and the spin fluctuations.(2) Determination of the Cooper-pair spin state : By nuclear magnetic resonance (NMR), we determined that the triplet spins lie in the RuO_2 plane, but that they can be rotated by weak magnetic fields.(3) Confirmation of odd parity : We fabricated a pi-junction SQUID (Superconducting QUantum Interference Device) consisting of Sr_2RuO_4 and an s-wave superconductor AuIn, and demonstrated that the parity of the superconducting wave function of Sr_2RuO_4 is odd, a requirement for the spin-triplet superconductivity.(4) Construction of the theoretical framework of superconducting mechanisms : We have succeeded in constructing a general theoretical framework of superconducting mechanism based on Coulomb repulsion among the strongly correlated electrons. By applying it to a detailed realistic model of Sr_2RuO_4,we are able to derive that the spin-triplet pairing is more stable than other states.We also discovered superconductivity in silver-lead oxide, Ag_5Pb_2O_6,clarified the mechanism of the Mott transition and orbital ordering in (Ca,Sr)_2RuO_4,and revealed the metamagnetic quantum critical phenomenon in Sr_3Ru_2O_7. We sponsored the international symposium on "Spin-Triplet Superconductivity and Ruthenate Physics", attended by most of the active researchers in this field, including over 20 researches from 8 abroad.