Description of the orbital magnetization in p-wave superconductors on the basis of the modern theory of polarization

超流氦-3（3 He-A）的轨道角动量的存在和大小已经讨论了50年，仍然是一个有争议的话题。悬而未决的问题是：“单个库珀对的角动量如何加起来成为超流凝聚体的轨道动量？“三重态超导体的类似问题，其中库珀对不仅有角动量和自旋，而且还有电荷，是轨道磁性的问题，具有类似的基本兴趣。为了阐明这些有趣的现象的物理学，我建议研究超导状态的Sr 2 RuO 4的基础上的一个现实的模型哈密顿量和轨道磁性的现代理论。它考虑了与电子的布洛赫态相关的“几何”（Berry）相。具有p对称性而不是更常见的s或d对称性的超导态的新奇之处在于，这里的库珀对不是单线态而是三线态，并且内部自旋和轨道角动量分别为S=1和L=1。在这种情况下，准粒子经历了一个自旋相关的配对势Delta_ss ′（k），并提供了一个独特的机会来研究它们的自旋和轨道自由度之间的相互作用。钌酸锶（Sr 2 RuO 4）是唯一的三重态配对和p波对称性的固态模拟在实验上得到很好的建立的系统。此外，还可以得到具有很长平均自由程（~10^-6 m）的高质量晶体，并且发现正常态是非常好的费米液体。总之，Sr 2 RuO 4是将现代轨道磁化理论应用于系统超导态的理想候选者。

The existence and magnitude of the orbital angular momentum in superfluid helium-3 (3He-A) has been under discussion for five decades and remains a subject of controversy. The open question is "How do the angular momenta of the individual Cooper Pairs add up to be the orbital momentum of the superfluid condensate?" The analogous problem for triplet superconductors, where the Cooper Pairs have not only angular momenta and spin but also charge, is that of orbital magnetism and is of similar fundamental interest. To shad light on the physics of these intriguing phenomena I propose to study the superconducting state of Sr2RuO4 on the basis of a realistic model Hamiltonian and the modern theory of orbital magnetism. It takes account of the "geometrical" (Berry) phases associated with Bloch sates of the electrons.The novelty of the superconducting state with p rather than the more usual s or d-symmetry is that here the cooper pairs are not singlets but triplets and have an internal spin and orbital angular momentum of S=1 and L=1, respectively. Under these circumstances the quasi-particles experience a spin dependent pairing potential Delta_ss´(k) and provide a unique opportunity to study the interaction between their spin and orbital degree of freedom in the context of a superfluid state with respect to charge.Strontium Ruthenate (Sr2RuO4) is the only system where triplet pairing and the solid-state analogue of p-wave symmetry is well established experimentally. Moreover, high quality crystals with very long mean free paths (~10^-6 m) are available and the normal state is found to be a very good Fermi liquid. All together Sr2RuO4 is the ideal candidate to apply the modern theory of orbital magnetization to the superconducting state of the system.