A. J. Fedro

Model of Ultrafast Intersystem Crossing in Photoexcited Transition-Metal Organic Compounds

The mechanism behind fast intersystem crossing in transition-metal complexes is shown to be a result of the dephasing of the photoexcited state to the phonon continuum of a different state with a significantly different transition metal-ligand distance. The coupling is a result of the spin-orbit interaction causing a change in the local moment. Recurrence to the initial state is prevented by the damping of the phonon oscillation. The decay time is faster than the oscillation frequency of the transition metal-ligand stretch mode, in agreement with experiment. For energies above the region where the strongest coupling occurs, a slower “leakage”-type decay is observed. If the photoexcited state is lower in energy than the state it couples to, then there is no decay.

Multiplet effects in the quasiparticle band structure of the f1-f2 Anderson model.

In this paper, we examine the mean-field electronic structure of the [ital f][sup 1][minus][ital f][sup 2] Anderson lattice model in a slave-boson approximation, which should be useful in understanding the physics of correlated metals with more than one [ital f] electron per site such as uranium-based heavy-fermion superconductors. We find that the multiplet structure of the [ital f][sup 2] ion acts to quench the crystal-field splitting in the quasiparticle electronic structure. This is consistent with experimental observations in such metals as UPt[sub 3].

Spin and hole excitation spectra in cuprate superconductors: An exact study of finite lattices with the inclusion of direct oxygen-oxygen hopping

We present results of an exact diagonalization study of the groundstate properties as well as spin and single-particle excitation spectra of a single mobile dopant induced hole in the strong coupling limit of the three-orbital Hubbard model in finite lattices with up to 16 copper lattice sites in the presence of the direct oxygen-oxygen transfer term with corresponding matrix element tpp. We show that the groundstate and low energy excited state properties are consistent with the proposal of Zhang and Rice (ZR) of a tightly bound stable Cu-O spin-hole singlet state even for the case of finite and physically relevant values of tpp indicating that the ZR state is relatively stable and persists even for moderate tpp.