167,786 research outputs found

    Product vacua with boundary states

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    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

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    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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