34 research outputs found
Spin tunnelling in mesoscopic systems
We study spin tunnelling in molecular magnets as an instance of a mesoscopic
phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel
splitting between various pairs of Zeeman levels in this molecule oscillates as
a function of applied magnetic field, vanishing completely at special points in
the space of magnetic fields, known as diabolical points. This phenomena is
explained in terms of two approaches, one based on spin-coherent-state path
integrals, and the other on a generalization of the phase integral (or WKB)
method to difference equations. Explicit formulas for the diabolical points are
obtained for a model Hamiltonian.Comment: 13 pages, 5 figures, uses Pramana style files; conference proceedings
articl
Glass Transition of Hard Sphere Systems: Molecular Dynamics and Density Functional Theory
The glass transition of a hard sphere system is investigated within the
framework of the density functional theory (DFT). Molecular dynamics (MD)
simulations are performed to study dynamical behavior of the system on the one
hand and to provide the data to produce the density field for the DFT on the
other hand. Energy landscape analysis based on the DFT shows that there appears
a metastable (local) free energy minimum representing an amorphous state as the
density is increased. This state turns out to become stable, compared with the
uniform liquid, at some density, around which we also observe sharp slowing
down of the relaxation in MD simulations.Comment: 5 pages, 5 figure