Showing papers by "Filip Kadlec published in 2023"
27 Mar 2023
TL;DR: In this article , an improved model for studying the interactions between dipole moments of water molecules confined in beryl crystals, inspired by recent NMR experiments, is presented. But the model is based on a local crystal potential with dihexagonal symmetry, leading to deflection from the $ab$ hexagonal crystallographic plane.
Abstract: We present an improved model for studying the interactions between dipole moments of water molecules confined in beryl crystals, inspired by recent NMR experiments. Our model is based on a local crystal potential with dihexagonal symmetry for the rotations of water dipole moments, leading to deflection from the $ab$ hexagonal crystallographic plane. This potential shape has significant implications for dipole ordering, which is linked to the non-zero projection of the dipole moment on the hexagonal $c$ axis. To reveal the tendency toward equilibrium-ordered states, we used a variational mean-field approximation, Monte Carlo simulations, and quantum tunneling. Our analysis reveals three types of equilibrium-ordered states: a purely planar dipole order with an antiparallel arrangement in the adjacent planes, a configuration with deflected dipole moments ordered in antiparallel directions, and a helical structure of the dipoles twisting along the $c$ axis.
TL;DR: In this paper , a time-resolved terahertz spectroscopy was used to show that electron-hole plasma expansion with velocities exceeding c/50 and lasting over 10ps at 300 K was demonstrated.
Abstract: Electron-hole plasma expansion with velocities exceeding c/50 and lasting over 10 ps at 300 K was evidenced by time-resolved terahertz spectroscopy. This regime, in which the carriers are driven over >30 μm is governed by stimulated emission due to low-energy electron-hole pair recombination and reabsorption of the emitted photons outside the plasma volume. At low temperatures a speed of c/10 was observed in the regime where the excitation pulse spectrally overlaps with emitted photons, leading to strong coherent light-matter interaction and optical soliton propagation effects.