A review of some new perspectives on the theory of superconducting Sr${}_2$RuO${}_4$

Abstract

The nature of the Cooper pairing in the paradigmatic unconventional superconductor Sr${}_2$RuO${}_4$ is an outstanding puzzle in condensed matter physics. Despite the tremendous efforts made in the past twenty-seven years, neither the pairing symmetry nor the underlying pairing mechanism in this material has been understood with clear consensus. This is largely due to the lack of a superconducting order that is capable of interpreting in a coherent manner the numerous essential experimental observations. At this stage, it may be desirable to reexamine the existing theoretical descriptions of superconducting Sr${}_2$RuO${}_4$. This review focuses on several recent developments that may provide some clues for future study. We highlight three separate aspects: 1) any pairing in the $E_u$ symmetry channel, with which the widely discussed chiral p-wave is associated, shall acquire a 3D structure due to spin-orbit entanglement; 2) if the reported Kerr effect is a superconductivity-induced intrinsic bulk response, the superconductivity must either exhibit a chiral character, or be complex mixtures of certain set of helical p-wave pairings; 3) when expressed in a multiorbital basis, the Cooper pairing could acquire numerous exotic forms that are inaccessible in single-orbital descriptions. The implications of each of these new perspectives are briefly discussed in connection with selected experimental phenomena.

8 pages, 3 figures and 2 tables. Invited topical review for Chinese Physics B. Published version

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Cited by in corpus (6)

• The fate of time-reversal symmetry breaking in UTe2
• Superconductivity in Correlated Multi-Orbital Systems with Spin-Orbit Coupling: Coexistence of Even- and Odd-Frequency Pairing and the Case of Strontium Ruthenate
• Constraints on the superconducting state of Sr${}_2$RuO${}_4$ from elastocaloric measurements
• Impact of random impurities on the anomalous Hall effect in chiral superconductors
• Quantum-geometry-induced anomalous Hall effect in nonunitary superconductors and application to Sr${}_2$RuO${}_4$
• Examining the possibility of chiral superconductivity in Sr${}_2$RuO${}_4$ and other compounds via applied supercurrent