Physics of Spin-Triplet Superconductivity

我们第一次坚定地确定了一个超导体，它的电子以自旋三重态配对，实际上存在。通过对Sr_2RuO_4超导体的广泛研究，我们在超导研究中获得了一些新的关键概念：（1）超导多能隙的确定：我们设计了一种确定每个费米面上超导能隙的方法。对于Sr_2RuO_4，我们根据自旋三重态对称性和自旋涨落来理解其多能隙结构的物理起源。(2)确定Cu对自旋态：通过核磁共振（NMR），我们确定了三重态自旋位于RuO_2平面内，但它们可以被弱磁场旋转。(3)奇宇称的确认：我们制作了由Sr_2RuO_4和s波超导体AuIn组成的π结SQUID（超导量子干涉器件），并证明了Sr_2RuO_4的超导波函数的宇称是奇的，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：我们成功地构建了基于强关联电子间库仑排斥的超导机制的一般理论框架。通过对Sr_2RuO_4详细的实际模型的研究，我们得到了自旋三重态对比其它态更稳定的结论，发现了银铅氧化物Ag_5Pb_2O_6的超导电性，阐明了（Ca，Sr）_2RuO_4的Mott跃迁和轨道有序机制，揭示了Sr_3Ru_2O_7的变磁量子临界现象。我们主办了“自旋三线态超导与钌酸盐物理”国际研讨会，该领域的大多数活跃研究人员参加了会议，其中包括来自8个国外的20多项研究。

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.