A unified theory of superconductivity and spin-density wave order in layered ruthenates

Significant interest has been paid to the ruthenate family of layered perovskites, with many recent works dedicated to understanding the superconducting (SC) state of the single layer Sr₂RuO₄, while other works have investigated the quantum criticality and spin-density wave (SDW) order observed in its sister material, the bilayer Sr₃Ru₂O₇.  In this work, we address a long-standing puzzle about the lack of superconductivity in Sr₃Ru₂O₇ despite their similar structures, and how to unify competing SC and SDW orders in this family. In previous works, we showed how interorbital spin-triplet pairings arise and their relevance to recent experimental observations in Sr₂RuO₄ [1-4].  We extend our model including both bilayer coupling and staggered octahedron rotations, and present a unified framework for these layered ruthenates. We also predict that the ideal Sr₃Ru₂O₇ without staggered octahedron rotations exhibits interorbital spin-triplet SC pairing.

 

[1] C. M. Puetter and H.-Y. Kee, EPL 98, 27010 (2012).

[2] A. W. Lindquist and H.-Y. Kee, PRR 2, 032055 (2020).

[3] J. Clepkens, A. W. Lindquist, and H.-Y. Kee, PRR 3, 013001 (2021).

[4] J. Clepkens, A. W. Lindquist, X. Liu, and H.-Y. Kee, PRB 104, 104512 (2021).