Related papers: The dynamic structure factor in impurity-doped spi…
We study the effect of impurities on the two types of spin-dimers in the hybrid chain/ladder spin 1/2 quantum magnet Sr$_{14}$Cu$_{24}$O$_{41}$. Four different impurities were used, namely, the non-magnetic Zn (0.0025 and 0.01 per Cu) and…
The static structure factor S(q) of frustrated spin-1/2 chains with isotropic exchange and a singlet ground state (GS) diverges at wave vector q_m when the GS has quasi-long-range order (QLRO) with periodicity 2\pi/q_m but S(q_m) is finite…
Low-lying excited states as well as the ground state of the spin-1 antiferromagnetic Heisenberg chain with a spin-1/2 impurity are studied by means of a method of numerical diagonalization. The isotropic nearest-neighbor exchange coupling…
Ground state and finite temperature properties of a system of coupled frustrated and/or dimerized spin-1/2 chains modeling e.g. the CuGeO$_3$ compound are reviewed. Special emphasis is put on the investigation of the role of impurity…
We consider the spin-1/2 Heisenberg XXZ chain in the regime of large Ising-like anisotropy $\Delta$. By a combination of duality and Jordan-Wigner transformations we derive a mapping to weakly interacting spinless fermions, which represent…
A computation of the dynamical structure factor of topologically disordered systems, where the disorder can be described in terms of euclidean random matrices, is presented. Among others, structural glasses and supercooled liquids belong to…
We compute the energies and transition probabilities for low excitations in the one dimensional antiferromagnetic spin-1/2 Heisenberg model by means of the recursion method. We analyse finite size effects in the euclidian time…
Nanoscale inhomogeneities and impurity clustering are often found to drastically affect the magnetic and transport properties in disordered/diluted systems, giving rise to rich and complex phenomena. However, the physics of these systems…
We study the effects of finite chemical potential and impurity scattering on dynamical fermion mass generation in (2+1)-dimensional quantum electrodynamics. In any realistic systems, these effects usually can not be neglected. The…
Effects of nonmagnetic impurity doping in a spin ladder system with a spin gap are investigated by the exact diagonalization as well as by the variational Monte Carlo calculations. Substantial changes in macroscopic properties such as…
Recently there has been a renewed interest in the spectra and role in dynamical properties of excited states of the spin-1/2 Heisenberg antiferromagnetic chain in longitudinal magnetic fields associated with Bethe strings. The latter are…
We have considered a numerical scheme for the calculation of the equilibrium properties of spin-1/2 XY chains. Within its frames it is necessary to solve in the last resort only the 2N\times 2N eigenvalue and eigenvector problem but not the…
We study the formation of antiferromagnetic correlations induced by impurity doping in anisotropic two-dimensional spin-Peierls systems. Using a mean-field approximation to deal with the inter-chain magnetic coupling, the intra-chain…
We investigate quantum impurity problems, where a local magnetic moment is coupled to the spin density of a bosonic environment, leading to bosonic versions of the standard Kondo and Anderson impurity models. In a physical situation, these…
The Kondo effect in a one-dimensional spin-1/2 XXZ model in the gapless XY regime (-1<Delta<=1) is studied both analytically and numerically. In our model an impurity spin (S=1/2) is coupled to a single spin in the XXZ spin chain.…
The dynamical dimer structure factor is an observable probing spin-singlet excitations of quantum magnets distinct from those commonly studied by the spin structure factor. We report the dimer response for the extended spin-$1/2$…
Using the density matrix renormalization group technique, we study the ground state phase diagram and other low-energy properties of an isotropic antiferromagnetic spin-half chain with both dimerization and frustration, i.e., an alternation…
The S=1/2 Heisenberg spin chain compound SrCuO2 doped with different amounts of nickel (Ni), palladium (Pd), zinc (Zn) and cobalt (Co) has been studied by means of Cu nuclear magnetic resonance (NMR). Replacing only a few of the S=1/2 Cu…
Velocity and density structure factors are measured over a hydrodynamic range of scales in a horizontal quasi-2d fluidized granular experiment, with packing fractions $\phi\in[10%,40%]$. The fluidization is realized by vertically vibrating…
We study the spin-1/2 antiferromagnetic Heisenberg chain in both uniform and (perpendicular) staggered magnetic fields using the density-matrix renormalization-group method. This model has been shown earlier to describe the physics of the…