Identify the microscopic scattering process governing gap relaxation

Identify the microscopic scattering process responsible for the 25-ps quasiparticle timescale governing superconducting gap relaxation in CsV3Sb5.

Background

The ultrasonic attenuation data are well described by Landau–Khalatnikov order-parameter relaxation with a characteristic microscopic timescale of approximately 25 ps. This timescale is much longer than the elastic scattering time inferred from resistivity, approximately 0.6 ps, and is comparable to the inelastic scattering time estimated from thermal transport, approximately 26 ps.

The comparison supports inelastic scattering as the simplest explanation, but the paper does not establish the specific microscopic process responsible for the relaxation. Possible interpretations include exceptionally strong inelastic scattering in a conventional s-wave state or unusually weak sensitivity to elastic disorder in an unconventional state.

References

The remaining question is what microscopic process is associated with the extracted τ_N = 25 ps.

— Out-of-equilibrium relaxation dynamics of the superconducting order parameter in CsV$_3$Sb$_5$  (2609.11686 - Shragai et al., 10 Sep 2026) in Analysis of the relaxation timescale, paragraph beginning “The remaining question is what microscopic process”