2,106 research outputs found
Phase diagram of the alternating-spin Heisenberg chain with extra isotropic three-body exchange interactions
For the time being isotropic three-body exchange interactions are scarcely
explored and mostly used as a tool for constructing various exactly solvable
one-dimensional models, although, generally speaking, such competing terms in
generic Heisenberg spin systems can be expected to support specific quantum
effects and phases. The Heisenberg chain constructed from alternating S=1 and
sigma=1/2 site spins defines a realistic prototype model admitting extra
three-body exchange terms. Based on numerical density-matrix renormalization
group (DMRG) and exact diagonalization (ED) calculations, we demonstrate that
the additional isotropic three-body terms stabilize a variety of
partially-polarized states as well as two specific non-magnetic states
including a critical spin-liquid phase controlled by two Gaussinal conformal
theories as well as a critical nematic-like phase characterized by dominant
quadrupolar S-spin fluctuations. Most of the established effects are related to
some specific features of the three-body interaction such as the promotion of
local collinear spin configurations and the enhanced tendency towards
nearest-neighbor clustering of the spins. It may be expected that most of the
predicted effects of the isotropic three-body interaction persist in higher
space dimensions.Comment: 13 pages, 17 figures, submitte
Algebraic bosonization: the study of the Heisenberg and Calogero-Sutherland models
We propose an approach to treat (1+1)--dimensional fermionic systems based on
the idea of algebraic bosonization. This amounts to decompose the elementary
low-lying excitations around the Fermi surface in terms of basic building
blocks which carry a representation of the W_{1+\infty} \times {\overline
W_{1+\infty}} algebra, which is the dynamical symmetry of the Fermi quantum
incompressible fluid. This symmetry simply expresses the local particle-number
current conservation at the Fermi surface. The general approach is illustrated
in detail in two examples: the Heisenberg and Calogero-Sutherland models, which
allow for a comparison with the exact Bethe Ansatz solution.Comment: 51 pages, plain LaTe
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