Znc. Ha et Fdm. Haldane, SQUEEZED STRINGS AND YANGIAN SYMMETRY OF THE HEISENBERG CHAIN WITH LONG-RANGE INTERACTION, Physical review. B, Condensed matter, 47(19), 1993, pp. 12459-12469
The exact and complete set of highest-weight eigenstates of the finite
-size SU(n) Heisenberg chain with inverse-square exchange (ISE) axe co
nstructed using the occupation-number representation of the ''strings,
'' which can be considered as the unbroken resonating-valence bonds. T
he string description, which is believed to be exact only in the therm
odynamic limit for the Bethe ansatz solvable models, becomes exact for
any size ISE model due to the squeezing effect of the strings in the
ISE limit. This feature provides a basis for the realization of the Ya
ngian symmetry in the ISE model.