We consider the ground states of the ferromagnetic XXZ chain with spin up boundary conditions in sectors with a fixed number of down spins. This forces the existence of a droplet of down spins in the system. We find the exact energy and the states that describe these droplets in the limit of an infinite number of down spins. We also prove that the droplet states, which were known to be separate...

A simple modification of the standard Renormalization Group (RG) technique for the study of quantum spin systems is introduced. By applying this method to the xxz spin 1 2 Heisenberg chain, we obtain the ground state energy with much higher accuracy than the standard RG.

For a 3-qubit Heisenberg model in a uniform magnetic field, the pairwise thermal entanglement of any two sites is identical due to the exchange symmetry of sites. In this paper we consider the effect of a non-uniform magnetic field on the Heisenberg model, modeling a magnetic impurity on one site. Since pairwise entanglement is calculated by tracing out one of the three sites, the entanglement ...

The density matrix renormalization group method is generalized to one dimensional random systems. Using this method, the energy gap distribution of the spin-1/2 random antiferromagnetic Heisenberg chain is calculated. The results are consistent with the predictions of the renormalization group theory demonstrating the effectiveness of the present method in random systems. The possible applicati...

We study the boundary impurity-induced critical behavior in an integrable SU(2)-invariant model consisting of an open Heisenberg chain of arbitrary spin-S (Takhatajian-Babujian model) interacting with an impurity of spin ~ S′ located at one of the boundaries. For S = 1/2 or S′ = 1/2, the impurity interaction has a very simple form J ~ S1 · ~ S′ which describes the deformed boundary bond between...

We compute specific heat of the antiferromagnetic spin2 Heisenberg model on the kagome lattice. We use a recently introduced technique to analyze high-temperature series expansion based on the knowledge of high-temperature series expansions, the total entropy of the system and the low-temperature expected behavior of the specific heat, as well as the ground-state energy. In the case of the kago...

We calculate the low temperature asymptotics of a function γ that generates the temperature dependence of all static correlation functions of the isotropic Heisenberg chain.

Geometrically frustrated magnetic molecules have attracted a lot of interest in the field of molecular magnetism as well as frustrated Heisenberg antiferromagnets. In this article we demonstrate how an approximate diagonalization scheme can be used in order to obtain thermodynamic and spectroscopic information about frustrated magnetic molecules. To this end we theoretically investigate an anti...

Time-dependent spin-autocorrelation functions at T = oo for the classical Heisenberg magnet in dimensions d = 1,2 and 3 are investigated by computer simulations. For the equivalent-neighbor Heisenberg model, the autocorrelation function is calculated analytically. Local spin fluctuations in magnetic insulators at high temperature spread rather slowly and persist over appreciable times and dista...

We present the results of exact diagonalization calculations of the isolated and isothermal on-site static susceptibilities in the anisotropic extended Heisenberg model on a linear chain with periodic boundary conditions. Based on the ergodicity considerations we conclude that the isothermal susceptibility will diverge as T → 0 both in finite clusters and in the bulk system in two non-ergodic r...