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Product vacua with boundary states
We introduce a family of quantum spin chains with nearest-neighbor
interactions that can serve to clarify and refine the classification of gapped
quantum phases of such systems. The gapped ground states of these models can be
described as a product vacuum with a finite number of particles bound to the
edges. The numbers of particles, n_L and n_R, that can bind to the left and
right edges of the finite chains serve as indices of the particular phase a
model belongs to. All these ground states, which we call Product Vacua with
Boundary States (PVBS) can be described as Matrix Product States (MPS). We
present a curve of gapped Hamiltonians connecting the AKLT model to its
representative PVBS model, which has indices n_L=n_R=1. We also present
examples with n_L=n_R=J, for any integer J\geq 1, that are related to a
recently introduced class of SO(2J+1)-invariant quantum spin chains.Comment: New section on SO(2J+1)-invariant model
Edge electron states for quasi-one-dimensional organic conductors in the magnetic-field-induced spin-density-wave phases
We develop a microscopic picture of the electron states localized at the
edges perpendicular to the chains in the Bechgaard salts in the quantum Hall
regime. In a magnetic-field-induced spin-density-wave state (FISDW)
characterized by an integer N, there exist N branches of chiral gapless edge
excitations. Localization length is much longer and velocity much lower for
these states than for the edge states parallel to the chains. We calculate the
contribution of these states to the specific heat and propose a time-of-flight
experiment to probe the propagating edge modes directly.Comment: 4 pages, 2 figures. V.2: Minor changes to the final version published
in PR
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