Hydrodynamic Limit for the Spin Dynamics of the Heisenberg Chain (2009)
Grossjohann, Simon, Brenig, Wolfram
We show that Quantum-Monte-Carlo calculations of the dynamic structure factor of the isotropic spin-1/2 antiferromagnetic chain at intermediate temperatures corroborate a picture of diffusive spin...
Plaquette Order in the J1-J2-J3 model: a series expansion analysis (2008)
Arlego, Marcelo, Brenig, Wolfram
Series expansion based on the flow equation method is employed to study the zero temperature properties of the spin-1/2 J1-J2-J3 antiferromagnet in two dimensions. Starting from the exact limit of...
Choi, Kwang-Yong, Nojiri, Hiroyuki, Dalal, Naresh S., Berger, Helmuth, Brenig, Wolfram, Lemmens, Peter
We report on the magnetic excitation spectrum of the coupled spin tetrahedral system Cu$_{2}$Te$_{2}$O$_{5}$Cl$_{2}$ using Raman scattering on single crystals. The transition to an ordered state at...
Perkins, Natalia, Brenig, Wolfram
We investigate two-magnon Raman scattering from the $S=1/2$ Heisenberg antiferromagnet on the triangular lattice, considering both the effect of renormalization of the one-magnon spectrum by 1/S...
Static Holes in the Geometrically Frustrated Bow Tie Ladder (2007)
Martins, George B., Brenig, Wolfram
We investigate the doping of a geometrically frustrated spin ladder with static holes by a complementary approach using exact diagonalization and quantum dimers. Results for thermodynamic properties,...
Order from Disorder in the Two-Dimensional Kondo-Necklace (2006)
We analyze the effects of site-dilution disorder on the thermodynamic properties of the two-dimensional Kondo necklace using finite-temperature stochastic series expansion. Results will be discussed...
Wither the sliding Luttinger liquid phase in the planar pyrochlore (2006)
Arlego, Marcelo, Brenig, Wolfram
Using series expansion based on the flow equation method we study the zero temperature properties of the spin-1/2 planar pyrochlore antiferromagnet in the limit of strong diagonal coupling. Starting...
Investigation of the oxohalogenide Cu4Te5O12Cl4 with weakly coupled Cu(II) tetrahedra (2006)
Takagi, Rie, Johnsson, Mats, Gnezdilov, Vladimir, Kremer, Reinhard K., Brenig, Wolfram, Lemmens, Peter
The crystal structure of the copper(II) tellurium(IV) oxochloride Cu$_{4}$Te$_{5}$O$_{12}$Cl$_{4}$ (Cu-45124) is composed of weakly coupled tetrahedral Cu clusters and shows crystallographic...
Series expansion analysis of a tetrahedral cluster spin chain (2005)
Arlego, Marcelo, Brenig, Wolfram
Using series expansion by continuous unitary transformations we study the magnetic properties of a frustrated tetrahedral spin-1/2 chain. Starting from the limit of isolated tetrahedra we analyze the...
Finite temperature properties of the two-dimensional SU(2) Kondo-necklace (2005)
We analyse several thermodynamic properties of the two-dimensional Kondo necklace using finite-temperature stochastic series expansion. In agreement with previous zero-temperature findings the model...
Spin- and Charge Excitations of the Triangular Hubbard-Model: a FLEX-Study (2003)
Renner, Marcus, Brenig, Wolfram
A study of the quasi-particle excitations and spin fluctuations in the one-band Hubbard-model on the triangular lattice with nearest- and next-nearest-neighbor hopping is presented. Using the...
Thermodynamic properties of ferromagnetic mixed-spin chain systems (2003)
Fukushima, Noboru, Honecker, Andreas, Wessel, Stefan, Brenig, Wolfram
Using a combination of high-temperature series expansion, exact diagonalization and quantum Monte Carlo, we perform a complementary analysis of the thermodynamic properties of quasi-one-dimensional...
On the valence-bond solid phase of the crossed-chain quantum spin model (2003)
Brenig, Wolfram, Grzeschik, Matthias
Using a series expansion based on the flow-equation method we study the ground state energy and the elementary triplet excitations of a generalized model of crossed spin-1/2 chains starting from the...
Spin dynamics of a tetrahedral cluster magnet (2002)
We study the magnetism of a lattice of coupled tetrahedral spin-1/2 clusters which might be of relevance to the tellurate compounds Cu2Te2O5X2, with X=Cl, Br. Using the flow equation method we...
Planar pyrochlore: a strong-coupling analysis (2001)
Brenig, Wolfram, Honecker, Andreas
Recent investigations of the two-dimensional spin-1/2 checkerboard lattice favor a valence bond crystal with long range quadrumer order [J.-B. Fouet et al., preprint cond-mat/0108070]. Starting from...
Two-hole dynamics in spin ladders (2001)
Jurecka, Christoph, Brenig, Wolfram
We present an analytic theory for the energy spectrum of a two-leg spin ladder doped with two holes. Starting from a pseudo-fermion-bond-boson representation of the corresponding $t_{1,2}-J_{1,2}$...
Magnetism of a tetrahedral cluster spin-chain (2001)
Brenig, Wolfram, Becker, Klaus W.
We discuss the magnetic properties of a dimerized and completely frustrated tetrahedral spin-1/2 chain. Using a combination of exact diagonalization and bond-operator theory the quantum phase diagram...
Raman cross section of spin ladders (2001)
Jurecka, Christoph, Gruetzun, Verena, Friedrich, Andreas, Brenig, Wolfram
We demonstrate that a two-triplet resonance strongly renormalizes the Raman spectrum of two-leg spin ladders and moreover suggest this to be the origin of the asymmetry of the magnetic Raman...
Bond operator mean field theory of the half filled Kondo lattice model (2001)
Jurecka, Christoph, Brenig, Wolfram
We present a bond-operator mean field theory for the Kondo lattice model at half filling in two (2D) and three (3D) dimensions. A continuous quantum phase transition from an antiferromagnetic to a...
Magnetism of a tetrahedral cluster-chain (2001)
Brenig, Wolfram, Becker, Klaus W., Lemmens, Peter
Magnetic properties of a completely frustrated tetrahedral chain are briefly summarized. Using exact diagonalization, and bond-operator theory results for the ground-state phase diagram, the...
Magnetic properties of a spin-1/2 quadrumer chain (2000)
Honecker, Andreas, Brenig, Wolfram
We study a novel S=1/2 cluster chain Hamiltonian which has recently been proposed in the context of the charge ordered low-temperature phase of alpha'-NaV2O5. We perform a detailed investigation of...
Single-hole dynamics in dimerized and frustrated spin-chains (2000)
Jurecka, Christoph, Brenig, Wolfram
We present a unified account for the coupled single-hole- and spin-dynamics in the spin-gap phase of dimerized and frustrated spin-chains and two-leg spin ladders. Based on the strong dimer-limit of...
Dzyaloshinskii-Moriya interaction in NaV$_2$O$_5$: a microscopic study (2000)
Valenti, Roser, Gros, Claudius, Brenig, Wolfram
We present a unified account of magnetic exchange and Raman scattering in the quasi-one-dimensional transition-metal oxide NaV$_2$O$_5$. Based on a cluster-model approach explicit expressions for the...
Crystal Field, Magnetic Anisotropy and Excitations in Rare-Earth Hexaborides (1999)
Uimin, Gennadi, Brenig, Wolfram
We clarify the role of crystalline electric field (CEF) induced magnetic anisotropy in the ground state and spin-wave spectrum of cubic rare-earth materials with dominating isotropic magnetic...
Anisotropic Scattering Rates in the t-t'-U Hubbard Model (1997)
Altmann, Joachim, Brenig, Wolfram, Kampf, Arno P.
We have investigated the evolution of the electronic properties of the t-t'-U Hubbard model with hole doping and temperature. Due to the shape of the Fermi surface, scattering from short wavelength...
Magnetic Excitations in quasi two-dimensional Spin-Peierls Systems (1997)
A study is presented of a two-dimensional frustrated and dimerized quantum spin-system which models the effect of inter-chain coupling in a spin-Peierls compound. Employing a bond-boson method to...
Raman Scattering from Frustrated Quantum Spin Chains (1997)
Magnetic Raman scattering from a frustrated spin-1/2 Heisenberg-chain is considered with a focus on the uniform phase of the spin-Peierls compound CuGeO_3. The Raman intensity is analyzed in terms of...