Phase ordering of charge density waves traced by ultrafast low-energy electron diffraction

Ultrafast low-energy electron diffraction traces phase-ordering kinetics of charge density waves

We introduce ultrafast low-energy electron diffraction (ULEED) in backscattering for the study of structural dynamics at surfaces. Using a tip-based source of ultrashort electron pulses, we investigate the optically-driven transition between charge-density wave phases at the surface of 1T-TaS2. Employing spot-profile analysis enabled by the large transfer width of the instrument, we resolve the...

Space charge effects in ultrafast electron diffraction and imaging

Understanding space charge effects is central for the development of high-brightness ultrafast electron diffraction and microscopy techniques for imaging material transformation with atomic scale detail at the fs to ps timescales. We present methods and results for direct ultrafast photoelectron beam characterization employing a shadow projection imaging technique to investigate the generation ...

Energy dispersive x-ray diffraction of charge density waves via chemical filtering

X - Ray Diffraction from Pinned Charge Density Waves

We present an x-ray study of doped charge density waves systems. When a 2k f-charge density wave is strongly pinned to impurities, an interference effect gives rise to an asymmetry between the intensities of the +2k f and −2k f satellite reflections. Moreover, profile asymmetry of the satellite reflections indicates the existence of Friedel oscillations (FOs) around the defects. We have studied...

Theory of Low-Energy Electron Diffraction

A method for calculating the intensities of diffracted waves in low energy electron diffraction by crystals is proposed. The elastic multiple scattering is fully taken into account. The cellular method of KOHN and ROSTOKER in the band theory of metals is applied to the integral equation of the scattering by two dimensional lattices, particularly by monatomic layers. The solution is expanded in ...