arXiv subjects

A. Shabalin

Publications and source records attributed to A. Shabalin.

6 recordsLinked to original sources

arXiv2025

Memory in strain-tuned insulator-metal-insulator sequence of transitions after photoexcitation in the Mott material V2O3

Memory effects during metal-insulator transitions in quantum materials reveal complex physics and potential for novel electronics mimicking biological neural systems. Nonetheless, understanding of memory and nonlinearity in sequential non-equilibrium transitions remains elusive as the full chain of transitions can involve features lasting anywhere from femtoseconds to microseconds. Here, we extend time-resolved x-ray Bragg diffraction to the dynamic range of timescales spanning 9 orders of magnitude to fully trace the pathways of photoexcited insulator-metal transition and the following relaxation through non-equilibrium metal-insulator transitions in epitaxial films of V2O3, a promising Mott material. We find 5 orders of magnitude variation in metal-insulator transition time, from nanoseconds to hundreds of microseconds, depending on pre-excitation phase state. We provide a theoretical explanation and simulations based on strain feedback to domain nucleation. The lingering transition is stretched in time by memory of spatial and energy heterogeneity and, contrary to known memory effects in vanadium oxides commonly described by power laws, follows an extremely (factor below 0.2) stretched exponential. The induced dramatic slowdown in the light-driven highly correlated system signifies unusually high heterogeneity of transition barriers similar to biological systems, and demonstrates importance of non-local correlations of structure in evolution of transitional phases in quantum materials.

cond-mat.mtrl-sci↗

arXiv2014

Characterization of Spatial Coherence of Synchrotron Radiation with Non-Redundant Arrays of Apertures

We present a method to characterize the spatial coherence of soft X-ray radiation from a single diffraction pattern. The technique is based on scattering from non-redundant arrays (NRA) of slits and records the degree of spatial coherence at several relative separations from one to 15 microns, simultaneously. Using NRAs we measured the transverse coherence of the X-ray beam at the XUV X-ray beamline P04 of the PETRA III synchrotron storage ring as a function of different beam parameters. To verify the results obtained with the NRAs additional Young's double pinhole experiments were conducted and show good agreement.

physics.optics↗

arXiv2014

Intensity interferometry of single x-ray pulses from a synchrotron storage ring

We report on measurements of second-order intensity correlations at the high brilliance storage ring PETRA III using a prototype of the newly developed Adaptive Gain Integrating Pixel Detector (AGIPD). The detector recorded individual synchrotron radiation pulses with an x-ray photon energy of 14.4 keV and repetition rate of about 5 MHz. The second-order intensity correlation function was measured simultaneously at different spatial separations that allowed to determine the transverse coherence length at these x-ray energies. The measured values are in a good agreement with theoretical simulations based on the Gaussian Schell-model.

physics.optics↗

arXiv2013

Ptychography imaging of the phase vortices in the x-ray beam formed by nanofocusing lenses

We present the ptychography reconstruction of the x-ray beam formed by nanofocusing lenses (NFLs) containing a number of phase singularities (vortices) in the vicinity of the focal plane. As a test object Siemens star pattern was used with the finest features of 50 nm for ptychography measurements. The extended ptychography iterative engine (ePIE) algorithm was applied to retrieve both complex illumination and object functions from the set of diffraction patterns. The reconstruction revealed the focus size of 91.4$\pm$1.1 nm in horizontal and 70$\pm$0.3 nm in vertical direction at full width at half maximum (FWHM). The complex probe function was propagated along the optical axis of the beam revealing the evolution of the phase singularities.

physics.optics↗

arXiv2013

X-ray cross-correlation analysis of liquid crystal membranes in the vicinity of hexatic-smectic phase transition

We present an x-ray study of liquid crystal membranes in the vicinity of hexatic-smectic phase transition by means of angular x-ray cross-correlation analysis (XCCA). By applying two-point angular intensity cross-correlation functions to the measured series of diffraction patterns the parameters of bond-orientational (BO) order in hexatic phase were directly determined. The temperature dependence of the positional correlation lengths was analyzed as well. The obtained correlation lengths show larger values for the higher-order Fourier components of BO order. These findings indicate a strong coupling between BO and positional order that has not been studied in detail up to now.

cond-mat.soft↗

arXiv2013

Hanbury Brown and Twiss interferometry at a free-electron laser

We present measurements of second- and higher-order intensity correlation functions (so-called Hanbury Brown and Twiss experiment) performed at the free-electron laser (FEL) FLASH in the non-linear regime of its operation. We demonstrate the high transverse coherence properties of the FEL beam with a degree of transverse coherence of about 80% and degeneracy parameter of the order 10^9 that makes it similar to laser sources. Intensity correlation measurements in spatial and frequency domain gave an estimate of the FEL average pulse duration of 50 fs. Our measurements of the higher-order correlation functions indicate that FEL radiation obeys Gaussian statistics, which is characteristic to chaotic sources.

physics.optics↗