Abstract
How materials evolve at thermal equilibrium and under external excitations at small length and time scales is crucial to the understanding and control of material properties. X-ray photon correlation spectroscopy (XPCS) at X-ray free electron laser (XFEL) facilities can in principle capture dynamics of materials that are substantially faster than a millisecond. However, the analysis and interpretation of XPCS data is hindered by the strongly fluctuating X-ray intensity from XFELs. Here we examine the impact of pulse-to-pulse intensity fluctuations on sequential XPCS analysis. We show that the conventional XPCS analysis can still faithfully capture the characteristic time scales, but with substantial decrease in the signal-to-noise ratio of the g2 function and increase in the uncertainties of the extracted time constants. We also demonstrate protocols for improving the signal-to-noise ratio and reducing the uncertainties.
Highlights
The evolution of solid-state materials at equilibrium and under external perturbations is crucial to understanding and controlling critical electronic properties in a wide range of materials, such as ferroelectrics [1], quasi-two-dimensional materials [2], and superconductors [3].Numerous studies have focused on the relationships between the crystal and electronic structures [4,5].Historically, such insights have primarily been gained in terms of average atomic positions and electronic densities of the material, while the importance of meso- and nanoscale heterogeneities ubiquitous in realistic functional and quantum materials has come to light more recently
The total number of frames is chosen to be on the same order as what can be obtained in a realistic X-ray photon correlation spectroscopy (XPCS) experiment at European X-ray free electron laser (XFEL) and Linac Coherent Light Source (LCLS)-II at the moment and in the near future
Our simulations aim to recreate these aspects of an XFEL-XPCS data set to assess and minimize their impact on data analysis, first by considering the effect of uniformly scaled low intensities on XPCS analysis, by incorporating XFEL-like intensity fluctuations of the incident beam
Summary
Numerous studies have focused on the relationships between the crystal and electronic structures [4,5]. Such insights have primarily been gained in terms of average atomic positions and electronic densities of the material, while the importance of meso- and nanoscale heterogeneities ubiquitous in realistic functional and quantum materials has come to light more recently. In a class of ferroelectric materials known as “relaxors”, polar nano regions (PNRs)—nano-size ferroelectric domains—are thought to be responsible for the observed 1000-fold increase in dielectric permittivity [8,9,10] with a frequency dependence spanning from Hz to MHz and beyond. In the realm of quantum materials, the domain walls in otherwise static charge-density-wave materials can be depinned by applying mild electric
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