Revealing Non-equilibrium and Relaxation in Warm Dense Matter

TL;DR

This paper introduces the imaginary time correlation function (ITCF) technique as a highly sensitive method to detect and quantify non-equilibrium states in warm dense matter using time-resolved x-ray scattering, enabling real-time relaxation tracking.

Contribution

The paper demonstrates the effectiveness of the ITCF technique in identifying non-equilibrium in warm dense matter without relying on models, advancing experimental diagnostics.

Findings

ITCF is highly sensitive to small non-equilibrium electron fractions.

ITCF can trace non-equilibrium relaxation from femtoseconds to tens of picoseconds.

Modern laser and detector setups can utilize ITCF for real-time non-equilibrium analysis.

Abstract

Experiments creating extreme states of matter almost invariably create non-equilibrium states. These are very interesting in their own right but need to be understood even if the ultimate goal is to probe high-pressure or high-temperature equilibrium properties like the equation of state. Here, we report on the capabilities of the newly developed imaginary time correlation function (ITCF) technique [1] to detect and quantify non-equilibrium in pump-probe experiments fielding time resolved x-ray scattering diagnostics. We find a high sensitivity of the ITCF even to a small fraction of non-equilibrium electrons in the Wigner distribution. The behavior of the ITCF technique is such that modern lasers and detectors should be able to trace the non-equilibrium relaxation from tens of femto-seconds to several 10s of picoseconds without the need for a model.