arXiv subjects

Chae Woo Ryu

Publications and source records attributed to Chae Woo Ryu.

3 recordsLinked to original sources

arXiv2026

Real-Space Dynamic Electron Correlation in Beryllium

Electron correlation in solid has a major impact on material properties. However, it has been studied mainly by theory, with very limited direct experimental investigations. Here, we demonstrate that dynamic electron correlation function can be experimentally measured using inelastic X-ray scattering on polycrystalline beryllium. The data are expressed as the energy-resolved dynamic pair-distribution function. Our results confirm the size of the exchange-correlation hole as ~2 Å, consistent with theoretical expectations. However, at the plasmon energy of ~21 eV, the exchange-correlation hole is extended up to 4-5 Å, suggesting a unique influence of the dynamic plasmon state.

cond-mat.other↗

arXiv2022

Medium-Range Atomic Correlation in Simple Liquids. III. Density Wave Theory

Elucidating the atomic structure of liquid and glass is one of the important open questions in condensed matter physics. In the conventional bottom-up approach one starts with focusing on an atom and the short-range order of its neighboring atoms, and the global structure is described in terms of overlapping local clusters of atoms as building units. However, this local approach fails to explain the strong drive to form the medium-range order which is distinct in nature from the short-range order. We propose an even-handed scheme with an additional top-down approach. In the top-down approach one starts with a high-density gas state and seeks to minimize the global potential energy through density waves. The local bottom-up and global top-down driving forces are not compatible, and the competition and compromise between them result in a final structure with the medium-range order. The density waves are pinned to atoms through the phase factors and amplitudes which reflect atomic dynamics. This even-handed approach provides a more intuitive explanation of the structure of simple liquid and glass and its relation to properties of liquid, such as viscosity and fragility.

cond-mat.dis-nn↗

arXiv2020

Split-pulse X-ray photon correlation spectroscopy with seeded X-rays from X-ray laser to study atomic-level dynamics

With their brilliance and temporal structure, X-ray free-electron laser can unveil atomic-scale details of ultrafast phenomena. Recent progress in split-and-delay optics (SDO), which produces two X-ray pulses with time-delays, offers bright prospects for observing dynamics at the atomic-scale. However, their insufficient pulse energy has limited its application either to phenomena with longer correlation length or to measurement with a fixed delay-time. Here we show that the combination of the SDO and self-seeding of X-rays increases the pulse energy and makes it possible to observe the atomic-scale dynamics in a timescale of picoseconds. We show that the speckle contrast in scattering from water depends on the delay-time as expected. Our results demonstrate the capability of measurement using the SDO with seeded X-rays for resolving the dynamics in temporal and spatial scales that are not accessible by other techniques, opening opportunities for studying the atomic-level dynamics.

physics.optics↗