Anisotropy and Strong-Coupling Effects on the Collective Mode Spectrum of Chiral Superconductors:
Application to Sr2RuO4
J. A. Sauls, Hao Wu and Suk Bum Chung
- Address: Department of Physics & Astronomy, Northwestern University, Evanston, IL 60208
- Date: March 2, 2015
Frontier in Physics 3:36 (2015)
Recent theories of Sr2RuO4 based on the interplay of strong interactions, spin-orbit coupling and
multi-band anisotropy predict chiral or helical ground states with strong anisotropy of the pairing states,
with deep minima in the excitation gap, as well as strong phase anisotropy for the chiral ground state.
We develop time-dependent mean field theory to calculate the Bosonic spectrum for the class of 2D chiral
superconductors spanning 3He-A to chiral superconductors with strong anisotropy. Chiral superconductors
support a pair of massive Bosonic excitations of the time-reversed pairs labeled by their parity under
charge conjugation. These modes are degenerate for 2D 3He-A. Crystal field anisotropy lifts the degeneracy.
Strong anisotropy also leads to low-lying Fermions, and thus to channels for the decay of the Bosonic modes.
Selection rules and phase space considerations lead to large asymmetries in the lifetimes and hybridization
of the Bosonic modes with the continuum of un-bound Fermion pairs. We also highlight results for the
excitation of the Bosonic modes by microwave radiation that provide clear signatures of the Bosonic modes
of an anisotropic chiral ground state.
- Comment: 11 pages, 8 figures. Presented as an invited talk at SCES14, Grenoble, France, July 2014.