Elementary excitations of Heisenberg ferrimagnetic spin chains

Article

关键词: BOND GROUND-STATES;    HALDANE-GAP;    MONTE-CARLO;    ALTERNATION;    FIELD;    ANTIFERROMAGNETS;    THETA=PI;    MODELS;   

DOI  :  10.1103/PhysRevB.57.13610

来源: SCIE

【 摘 要 】

We numerically investigate elementary excitations of the Heisenberg alternating-spin chains with two kinds of spins, 1 and 1/2, antiferromagnetically coupled to each other. Employing a recently developed efficient Monte Carlo technique as well as an exact-diagonalization method, we verify the spin-wave argument that the model exhibits two distinct excitations from the ground state which are gapless and gapped. The gapless branch shows a quadratic dispersion in the small-momentum region, which is of the ferromagnetic type. With the intention of elucidating the physical mechanism of both excitations, we make a perturbation approach from the decoupled-dimer limit. The gapless branch is directly related to spin 1's, while the gapped branch originates from cooperation of tbe two Binds of spins.

【 授权许可】

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