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

• Applicant: Dr. Martin Gradhand
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 195783728

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.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Hosts: Professor Dr. James Annett; Professor Dr. Balázs Gyõrffy