H . - J . Mikeska

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We investigate antiferromagnetic spin ladders with nonmagnetic impurities by variational and numerical (Lanczos and DMRG) methods. The interaction between the two unpaired spins opposite to the impurities is described by an effective exchange interaction Jeff , the magnitude of which depends on the impurity distance. The magnitude of Jeff is different for(More)
We investigate the phase diagram of antiferromagnetic spin ladders with additional exchange interactions on diagonal bonds by variational and numerical methods. These generalized spin ladders interpolate smoothly between the [Formula: see text] chain with competing nn and nnn interactions, the [Formula: see text] chain with alternating exchange and the(More)
We present results on the dynamics of the distorted diamond chain, S=1/2 dimers alternating with single spins 1/2 and exchange couplings J1 and J3 in between. The dynamics in the spin fluid (SF) and tetramer-dimer (TD) phases is investigated numerically by exact diagonalization for up to 24 spins. Representative excitation spectra are presented, both for(More)
TlCuCl3 has a singlet ground state with the excitation gap ∆ = 0.65 meV. The magnetic excitations in TlCuCl3 have been investigated by means of neutron inelastic scattering experiments. The constant-Q energy scan profiles were collected in the a∗ − c∗ plane. A well-defined single magnetic excitation mode was observed. The dispersion relations along four(More)
We investigate the phase diagram of antiferromagnetic spin ladders with additional exchange interactions on diagonal bonds by variational and numerical methods. These generalized spin ladders interpolate smoothly between the S = 1/2 chain with competing nn and nnn interactions, the S = 1/2 chain with alternating exchange and the antiferromagnetic S = 1(More)
TlCuCl3 has a singlet ground state with the excitation gap ∆ = 0.65 meV. The magnetic excitations in TlCuCl3 have been investigated by means of neutron inelastic scattering experiments. The constant-Q energy scan profiles were collected in the a∗ − c∗ plane. A well-defined single magnetic excitation mode was observed. The dispersion relations along four(More)
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