Multi-Orbital Superconductivity in SrTiO

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概要

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• We investigate the superconductivity in two-dimensional electron systems formed in SrTiO<inf>3</inf>nanostructures. Our theoretical analysis is based on the three-orbital model, which takes into account t_{\text{2g}} orbitals of Ti ions. Because of the interfacial breaking of mirror symmetry, a Rashba-type antisymmetric spin--orbit coupling arises from the cooperation of intersite and interorbital hybridyzation and atomic LS coupling. This model shows a characteristic spin texture and carrier density dependence of Rashba spin--orbit coupling through the orbital degree of freedom. Superconductivity is mainly caused by heavy quasiparticles consisting of d_{yz} and d_{zx} orbitals at high carrier densities. We find that the Rashba spin--orbit coupling stabilizes a quasi-one-dimensional superconducting phase caused by one of the d_{yz} or d_{zx} orbitals at high magnetic fields along interfaces. This quasi-one-dimensional superconducting phase is protected against paramagnetic depairing effects by the Rashba spin--orbit coupling and realizes a large upper critical field H_{\text{c2}} beyond the Pauli--Clogston--Chandrasekhar limit. This finding is consistent with an extraordinarily large upper critical field observed in SrTiO<inf>3</inf>/LaAlO<inf>3</inf>interfaces and its carrier density dependence. The possible coexistence of superconductivity and ferromagnetism in SrTiO<inf>3</inf>/LaAlO<inf>3</inf>interfaces may also be attributed to this quasi-one-dimensional superconducting phase.

• 2013-08-15

著者

• Yanase Youichi

  Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan

• Nakamura Yasuharu

  Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan

関連論文

• Spin--Orbit Coupling in Multilayer Superconductors with Charge Imbalance
• Spin Susceptibility in Non-Centrosymmetric Superconductors with Topological Transition of Fermi Surfaces
• Spin-Triplet Pairing State of Sr
• Multi-Orbital Superconductivity in SrTiO

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