Dynamical structure factors for dimerized spin systems

Abstract

We discuss the transition strength between the disordered ground state and the basic low-lying triplet excitation for interacting dimer materials by presenting theoretical calculations and series expansions as well as inelastic neutron scattering results for the material KCuCl 3 . We describe in detail the features resulting from the presence of two differently oriented dimers per unit cell and show how energies and spectral weights of the resulting two modes are related to each other. We present results from the perturbation expansion in the interdimer interaction strength and thus demonstrate that the wave vector dependence of the simple dimer approximation is modified in higher orders. Explicit results are given in 10 th order for dimers coupled in 1D, and in 2 nd order for dimers coupled in 3D with application to KCuCl 3 and TlCuCl 3 .

Finite-temperature dynamics of the spin-12bond alternating Heisenberg antiferromagnetic chain

“…These methods have established the existence of bound states of two excited dimers below the two magnon band, two singlets and two triplets 17 , for wave vectors close to π and energies and transition matrix elements for the one and two magnon bands have been obtained up to 13 th order 18 from series expansions. We remark that the analogous calculation including 3D interactions has only been done up to 3 rd order 19 . These results are in excellent agreement with experiments at low temperatures.…”

Electronic states of ultrathin Co layers on Cu

“…Recently the problem of surface alloy [1] becomes more important in the magnetic film growth since some properties of magnetic multilayered system are determined by the interfacial properties [2]. The surface alloying sometimes cannot be avoided when the temperature of the sample is raised.…”

Indium-Gallium Segregation inCuInxGa1−xSe2: AnAb Initio–Based Monte Carlo Study

“…The indices i and j run over all lattice sites and s m is −1 for In and +1 for Ga on lattice site m. Every figure is associated with a coefficient J that gives the energy contribution of the specific figure. Detailed descriptions of the CE method can be found in [12] and [11]. The coefficients of the expansion are fitted to ab-initio energies from electronic structure calculations.…”