paper

Dynamical T=0 correlations of the S=1/2 1D Heisenberg Anti-Ferromagnet with 1/r^2 exchange in a magnetic field

arXiv:cond-mat/9405043 · doi:10.1103/PhysRevB.50.6889

Abstract

We present a new selection rule for matrix elements of local spin operators in the ``Haldane-Shastry'' model. Based on this rule we extend a recent exact calculation \cite{H93} of the ground-state dynamical spin correlation function = and its Fourier-transform of this model to a finite magnetic field. In zero field, only {\it two-spinon} excitations contribute to the spectral function; in the (positively) partially-spin-polarized case, there are two types of elementary excitations: {\it spinons} () and {\it magnons} (). The magnons are divided into left- or right-moving branches. The only classes of excited states contributing to the spectral functions are: (I) two spinons, (II) two spinons + one magnon, (IIIa) two spinons + two magnons (moving in opposite directions), (IIIb) one magnon. The contributions to the various correlations are: : (I); : (I)+(II); : (I)+(II)+(III). In the zero-field limit there are no magnons, while in the fully-polarized case, there are no spinons. We discuss the relation of the spectral functions to correlations of the Calogero-Sutherland model at coupling .

29 pages, REVTEX v3.0, including 6 PostScript figures

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