Exotic Cooper pairing in multi-orbital models of Sr${}_2$RuO${}_4$

Abstract

The unconventional superconductivity in Sr${}_2$RuO${}_4$ continues to defy a unified interpretation. In this paper, we focus on some novel aspects of its superconducting pairing by exploiting the orbital degree of freedom in this material. The multi-orbital nature, combined with the symmetry of the orbitals involved, leads to a plethora of exotic Cooper pairings not accessible in single-orbital systems. Essential physics is illustrated first using a two-orbital model with $d_{xz}$- and $d_{yz}$-orbitals. We classify the gap functions according to the underlying lattice symmetries, analyze the effective theories of a few representative pairings, and make connections to Sr${}_2$RuO${}_4$ in the course. In particular, we show how spin-orbit coupling may entangle spin-triplet and spin-singlet pairings. For completeness, the classification is generalized to the three-orbital model involving the $d_{xy}$-orbital as well. The orbital-basis approach distinguishes from the itinerant-band description for Sr${}_2$RuO${}_4$, and hence offers an alternative perspective to investigate its enigmatic superconducting state.

7 pages, 1 figure and 2 tables. Published version

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Cited by in corpus (28)

• Recent progress on superconductors with time-reversal symmetry breaking
• Inhomogeneous time-reversal symmetry breaking in ${\mathrm{Sr}}_2\mathrm{Ru}{\mathrm{O}}_4$
• Superconducting state of Sr${}_2$RuO${}_4$ in the presence of longer-range Coulomb interactions
• Quantitative Theory of Triplet Pairing in the Unconventional Superconductor LaNiGa${}_2$
• Theory of Strain-Induced Magnetic Order and Splitting of $T_c$ and $T_{\mathrm{TRSB}}$ in Sr${}_2$RuO${}_4$
• Group-theoretic classification of superconducting states of Strontium Ruthenate
• Shadowed triplet pairings in Hund's metals with spin-orbit coupling
• Multiorbital singlet pairing and $d+d$ superconductivity
• Superconductivity in Correlated Multi-Orbital Systems with Spin-Orbit Coupling: Coexistence of Even- and Odd-Frequency Pairing and the Case of Strontium Ruthenate
• Distinct reduction of Knight shift in superconducting state of Sr${}_2$RuO${}_4$ under uniaxial strain
• Constraints on the superconducting state of Sr${}_2$RuO${}_4$ from elastocaloric measurements
• Higher angular momentum pairing states in Sr${}_2$RuO${}_4$ in the presence of longer-range interactions
• Superconductivity in multiorbital systems with repulsive interactions: Hund's pairing vs. spin-fluctuation pairing
• Hidden anomalous Hall effect in Sr${}_2$RuO${}_4$ with chiral superconductivity dominated by the Ru $d_{xy}$ orbital
• Multipole-fluctuation pairing mechanism of $d_{x^2-y^2}+ig$ superconductivity in Sr${}_2$RuO${}_4$
• Magnetically-textured superconductivity in elemental Rhenium
• Exotic interband pairing in multiband superconductors
• Inter-orbital p- and d-wave pairings between $d_{xz/yz}$ and $d_{xy}$ orbitals in Sr${}_2$RuO${}_4$
• Possibility of mixed helical p-wave pairings in Sr${}_2$RuO${}_4$
• Quantum-geometry-induced anomalous Hall effect in nonunitary superconductors and application to Sr${}_2$RuO${}_4$
• Degeneracy between even- and odd-parity superconductivity in the quasi-1D Hubbard model and implications for Sr2RuO4
• A review of some new perspectives on the theory of superconducting Sr${}_2$RuO${}_4$
• Possible two-component spin-singlet pairings in Sr2RuO4
• Spin-orbit-coupled superconductivity with spin-singlet non-unitary pairing
• Reconciling $\pi$ phase shift in Josephson junction experiments with even-parity superconductivity in Sr${}_2$RuO${}_4$
• Enhanced Spin-Orbit Coupling in a Correlated Metal
• Evolution of Interorbital Superconductor to Intraorbital Spin-Density Wave in Layered Ruthenates
• Quantum-geometry-induced intrinsic optical anomaly in multiorbital superconductors