Photon-recoil imaging: Expanding the view of nonlinear x-ray physics

Addressing the ultrafast coherent evolution of electronic wave functions has long been a goal of nonlinear x-ray physics. A first step toward this goal is the investigation of stimulated x-ray Raman scattering (SXRS) using intense pulses from an x-ray free-electron laser. Earlier SXRS experiments relied on signal amplification during pulse propagation through dense resonant media. By contrast, our method reveals the fundamental process in which photons from the primary radiation source directly interact with a single atom. We introduce an experimental protocol in which scattered neutral atoms rather than scattered photons are detected. We present SXRS measurements at the neon K edge and a quantitative theoretical analysis. The method should become a powerful tool in the exploration of nonlinear x-ray physics.

Anomalous Number Fluctuation Noise in Localized Transition Metal Dichalcogenide Layers: Generalization of McWhorter’s Mechanism

ABSTRACTThe mechanism of electrical noise in transition metal dichalcogenides (TMDCs) has mostly been attributed to charge carrier fluctuations between the oxide traps and the conducting channel, in accordance with the McWhorter model. However, the original McWhorter model was formulated for diffusive transport with conducting carriers having extended electronic wave functions. Our work serves to generalize the McWhorter mechanism to include strongly localized systems such as the TMDC family and provides an explanation for the unusual exponential behavior of noise magnitude with temperature.