Geant4 is a toolkit for the simulation of the passage of particles through matter. Its areas of application include high energy, nuclear and accelerator physics, as well as studies in medical and space science. In this article, the recent developments of Geant4, especially new functionalities and applications using parallel computing, are explained.
Cavity Quantum Electrodynamics (QED) studies the light-matter coupling in one of the simplest settings. Recently, the ultra- and deep-strong coupling regimes have been experimentally realized, where the coupling g is comparable or even greater than the transition energies of components such as cavity modes and atoms. We review the mysterious phenomenon in this regime caused by the anti-rotating terms in the coupling Hamiltonian.
Although the importance of the lattice vibration in organic crystals is recognized, experimental observation of the phonon in molecular crystals has been scarce. Here, we demonstrate the phonon dispersion measurement by means of the inelastic x-ray scattering technique assisted by the density functional theory calculation on the most studied high-mobility organic semiconductor, rubrene single crystal.
We propose a Jarzynski-type work relation for determining mixing free energy. It contains two kinds of work required in two alchemical protocols. We then evaluate the Gibbs factorial numerically by comparing the free energies of a mixture calculated from alchemical and non-alchemical procedures. Finally, we formulate the Gibbs factorial as a quasistatic work of classical systems defined by an operation of many-body potential with permutation symmetry.
Spin Hall (Nernst) effect has been recognized as a response of “spin current” to an electric field (a temperature gradient). However, “spin current” is ill defined in the presence of a spin-orbit coupling, which is the origin of these phenomena. Here, we propose a new formalism focusing on the spin accumulation at the boundaries. We consider the responses of spin to the gradients of the electric field and temperature gradient, and prove the generalized Mott relation between them and Onsager’s reciprocity relation. This formalism provides a new charge (heat)-spin conversion efficiency that can be evaluated by first-principles calculations.