Self-similar dynamics of order parameter fluctuations in pump-probe experiments

TL;DR

This paper presents a simple effective model explaining the universal slowing down and power-law relaxation of order parameter fluctuations in pump-probe experiments across various solids, highlighting prethermalized dynamics.

Contribution

It introduces a non-perturbative model capturing universal prethermalized dynamics and scaling behavior of collective modes after photoexcitation.

Findings

Universal power-law relaxation of order parameters

Dominance of long-wavelength transverse modes after strong quenches

Analytical computation of universal scaling exponents

Abstract

Upon excitation by a laser pulse, broken-symmetry phases of a wide variety of solids demonstrate similar order parameter dynamics characterized by a dramatic slowing down of relaxation for stronger pump fluences. Motivated by this recurrent phenomenology, we develop a simple non-perturbative effective model of dynamics of collective bosonic excitations in pump-probe experiments. We find that as the system recovers after photoexcitation, it shows universal prethermalized dynamics manifesting a power-law, as opposed to exponential, relaxation, explaining the slowing down of the recovery process. For strong quenches, long-wavelength over-populated transverse modes dominate the long-time dynamics; their distribution function exhibits universal scaling in time and space, whose universal exponents can be computed analytically. Our model offers a unifying description of order parameter fluctuations in a regime far from equilibrium, and our predictions can be tested with available time-resolved techniques.