Possible 'symmetry-imposed' near-nodal two-dimensional p-wave pairing in Sr$_2$RuO$_4$

Abstract

One key feature of the multi-orbital superconducting Sr2RuO4 is the presence of nodal or near-nodal quasiparticle excitations revealed in a wide variety of experiments. Typically, a nodal gap structure in a two-dimensional model would be inconsistent with the chiral or helical p-wave interpretations. However, we demonstrate that true gap nodes may emerge along the xand y-directions on the quasi-one-dimensional Fermi surfaces, if the multi-orbital chiral or helical p-wave pairings acquire peculiar forms wherein the dxz and dyz orbitals develop kyand kx-like pairings, respectively. Spin-orbit coupling η induces a near-nodal gap of order η 2 /W 2 ∆0, where ∆0 is the gap amplitude and W roughly the bandwidth. Provided the aforementioned pairing is predominant, the near-nodal gap structure is robust upon the inclusion of other multi-orbital pairings that share the same symmetries. In light of the recent experimental progresses, our proposal suggests that two-dimensional p-wave pairings may still be viable candidate ground states for Sr2RuO4. A near-nodal helical p-wave order, for example, may also be in line with the substantial drop in the NMR Knight shift under an in-plane magnetic field.

Possibility of mixed helical p-wave pairings in Sr$_2$RuO$_4$

“…For example, the presence of gapless excitations [66,[68][69][70][71] would place strong constraint on the detailed forms of the p-wave pairings. To this end, we take note of the multitude of possibilities made available by the multiorbital nature of this material [51][52][53][72][73][74][75][76][77][78][79][80].…”

A review of some new perspectives on the theory of superconducting Sr2RuO4 *

“…Indeed, developments set to exploit the multiorbital nature have already been undertaken, with a multitude of attempts to reconcile with various experiments. [97][98][99][100][101]…”

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

“…Such exotic possibilities readily prompt new ideas for Sr 2 RuO 4 . Indeed, developments set to exploit the multiorbital nature have already been undertaken, with a multitude of attempts to reconcile with various experiments [97][98][99][100][101] .…”