We have obtained deuterium NMR spin-echo spectra of crystalline DL-[gamma-2H6]valine, [S-methyl-2H3]-methionine, cyanoferrimyoglobin from sperm whale (Physeter catodon), containing deuteriomethyl groups at methionine-55 and methionine-131, and [gamma-2H6]valine-labeled bacteriorhodopsin in the purple membrane of Halobacterium halobium R1. By using 90-tau-beta 90 degrees (XY) and 90-tau-beta 0 d...

We examine dynamic quantities of a random spin-1/2 isotropic XY chain in a transverse field. The randomness is related to the sign of the nearest-neighbor exchange interaction and can be eliminated by a suitable transformation. As a result, the dynamic quantities for the random spin chain are related to the same dynamic quantities for the homogeneous spin chain. We use the available results for...

Using a new version of the density-matrix renormalization group we determine the phase diagram of a model of an antiferromagnetic Heisenberg spin chain where the spins interact with quantum phonons. A quantum phase transition from a gapless spin-fluid state to a gapped dimerized phase occurs at a nonzero value of the spin-phonon coupling. The transition is in the same universality class as that...

An interest in the theoretical study of quantum spin chains exhibiting spin–Peierls phases has incredibly grown since the discovery of the first inorganic spin–Peierls compound CuGeO3 (for a review see). Although the quantum Heisenberg model is usually used as an appropriate model to describe the spin–Peierls phase transition in the available materials some generic features can be clarified wit...

We investigate the topological quenching of spin tunneling in Mn12-acetate molecules with an applied magnetic field along the hard axis. The model Hamiltonian describing this system has a fourth-order term due to the tetragonal anisotroy. We treat this model using the discrete phase integral formalism in which the Schrödinger equation corresponding to the Hamiltonian becomes a nine-term recursi...

The paper presents a numerical approach for the calculation of thermodynamics and spin correlations for spin-2 XY chains. To illustrate the approach we performed exact finite-chain calculations of all time-dependent two-spin correlation functions for the spin-2 Ising chain in the transverse field. The computed correlation functions permit to evaluate the frequency-dependent susceptibilities and...

We consider the Super Yang–Mills/spin system map to construct the SU(2) spin bit model at the level of two loops in Yang–Mills perturbation theory. The model describes a spin system with chaining interaction. In the large N limit the model is shown to be reduced to the two loop planar integrable spin chain.

We consider the Super Yang–Mills/spin system map to construct the SU(2) spin bit model at the level of two loops in Yang–Mills perturbation theory. The model describes a spin system with chaining interaction. In the large N limit the model is shown to be reduced to the two loop planar integrable spin chain.

Through an h̄-expansion of the confined Calogero model with spin exchange interactions, we extract a generating function for the involutive conserved charges of the FrahmPolychronakos spin chain. The resulting conservation laws possess the spin chain yangian symmetry, although they are not expressible in terms of these yangians. 08/00 (revised: 02/01) 1 Work supported by NSERC (Canada) and FCAR ...