The superconducting state in Strontium Ruthenate is known to be of unconventional nature where the transition temperature can be enhanced by a uniaxial strain. After three decades of intensive research, several experiments probing its superconducting state remain unexplained. Among them is a recent Resonance Ultrasonic spectroscopy (RUS) and NMR knight shift experiment, that offer some insights into the structure of its superconducting order parameter.
Since the ultrasonic attenuation experiments are associated with the scattering of sound waves by quasiparticles, we discuss a microscopic model relevant towards understanding the normal state and superconducting state ultrasonic attenuation experiments in Sr2RuO4. We present some calculations on the decay rate of phonons for different sound wave modes.
We also briefly discuss our recent efforts towards understanding conductance experiments in magnetic topological insulator Mn2BiTe4 and in its heterostructure with s-wave superconductor 2H-NbSe2.