29 research outputs found
Ground state of a spin-1/2 Heisenberg-Ising two-leg ladder with XYZ intra-rung coupling
The quantum spin-1/2 two-leg ladder with an anisotropic XYZ Heisenberg
intra-rung interaction and Ising inter-rung interactions is treated by means of
a rigorous approach based on the unitary transformation. The particular case of
the considered model with X-X intra-rung interaction resembles a quantum
compass ladder with additional frustrating diagonal Ising interactions. Using
an appropriately chosen unitary transformation, the model under investigation
may be reduced to a transverse Ising chain with composite spins, and one may
subsequently find the ground state quite rigorously. We obtain a ground-state
phase diagram and analyze the interplay of the competition between several
factors: the XYZ anisotropy in the Heisenberg intra-rung coupling, the Ising
interaction along the legs, and the frustrating diagonal Ising interaction. The
investigated model shows extraordinarily diverse ground-state phase diagrams
including several unusual quantum ordered phases, two different disordered
quantum paramagnetic phases, as well as discontinuous or continuous quantum
phase transitions between those phases.Comment: 8 pages, 4 figure
Low-temperature thermodynamics of spin-1/2 orthogonal-dimer chain with Ising and Heisenberg interactions
We consider an exactly solvable version of the quantum spin-1/2
orthogonal-dimer chain with the Heisenberg intra-dimer and Ising inter-dimer
couplings. The investigated quantum spin system exhibits at zero temperature
fractional plateaux at 1/4 and 1/2 of the saturation magnetization and it has a
highly degenerate ground state at critical fields where the magnetization
jumps. We study the field dependence of the specific heat at low temperature.
The lattice-gas description is formulated in a vicinity of critical fields to
explain the low-temperature behaviour of specific heat.Comment: 2 pages, 1 figure, contribution to proceedings of CSMAG'13 conferenc
Jordan-Wigner approach to the frustrated spin one-half XXZ chain
The Jordan-Wigner transformation is applied to study the ground state
properties and dimerization transition in the chain. We
consider different solutions of the mean-field approximation for the
transformed Hamiltonian. Ground state energy and the static structure factor
are compared with complementary exact diagonalization and good agreement is
found near the limit of the Majumdar-Ghosh model. Furthermore, the ground state
phase diagram is discussed within the mean-field theory. In particular, we show
that an incommensurate ground state is absent for large in a fully
self-consistent mean-field analysis.Comment: final version to appear in Eur. Phys. J. B; 5 pages including 4
figures; some small extensions including additional reference