Interorbital <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math>- and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>d</mml:mi></mml:math>-wave pairings between <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>d</mml:mi><mml:mrow><mml:mi>x</mml:mi><mml:mi>z</mml:mi><mml:mo>/</mml:mo><mml:mi>y</mml:mi><mml:mi>z</mml:mi></mml:mrow></mml:msub></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>d</mml:mi><mml:mrow><mml:mi>x</mml:mi><mml:mi>y</mml:mi></mml:mrow></mml:msub></mml:math> orbitals in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Sr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">RuO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:math>
Weipeng Chen, Jin An
Abstract
We study the pairing symmetry of ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ through the group-theoretical approach. We emphasize the role of pairing interaction between the quasi-one-dimensional (Q1D) ${d}_{xz/yz}$ and quasi-two-dimensional (Q2D) ${d}_{xy}$ orbitals. It is found that two degenerate interorbital time-reversal-invariant(TRI) $p$-wave pairings, one spin singlet and the other spin triplet with out-of-plane $\mathbit{d}$ vector, could be the most promising candidates. Several important physical quantities are presented, including the near-nodal gap structure, the unchanged out-of-plane Knight shift, and no splitting of transition under strain, which are consistent with the experiments. In addition, these $p$-wave pairings shed light on resolving the contradiction between the time-reversal breaking and reduced in-plane Knight shift measurements. As the system reaches the Van Hove singularity under applied strain, the pairing symmetry would become a $d$-wave pairing mainly consisting of interorbital components, which could be responsible for the strained $3K$ phase.