Variational states for the spin-Peierls system

Spin-Peierls States of Quantum Antiferromagnets on the CaV4O9 Lattice.

We discuss the quantum paramagnetic phases of Heisenberg antiferromagnets on the 1/5-depleted square lattice found in CaV4O9. The possible phases of the quantum dimer model on this lattice are obtained by a mapping to a quantum-mechanical height model. In addition to the “decoupled” phases found earlier, we find a possible intermediate spin-Peierls phase with spontaneously-broken lattice symmet...

The spin-Peierls chain revisited

We extend previous analytical studies of the ground-state phase diagram of a one-dimensional Heisenberg spin chain coupled to optical phonons, which for increasing spin-lattice coupling undergoes a quantum phase transition from a gap-less to a gaped phase with finite lattice dimerisation. We check the analytical results against established four-block and new two-block density matrix renormalisa...

0 Superexchange and lattice distortions in the spin – Peierls system

We present a study of the nearest–neighbor (nn) and next–nearest–neighbor (nnn) exchange constants between magnetic Cu centers of the spin–Peierls material CuGeO 3. The dependence of these constants on the lattice parameters (modified e.g. by variation of temperature, pressure or doping) is calculated. Based on the observation that the bond angles are more susceptible than the bond lengths we p...

Frustrated spin-Peierls chains.

We study the phase diagram, ground state properties, and excitation gaps of a frustrated spin-Peierls chain, i.e. a spin-Peierls chain with both nearest neighbor exchange J1 and next nearest neighbor exchange J2. The phase diagram is calculated using a bosonization Renormalization-Group (RG) method. We propose a (bosonic) bond-operator mean field approximation to calculate the ground state prop...

Spin Peierls Effect in Spin Polarization of Fractional Quantum Hall States