78 research outputs found
Novel Order Parameter to Characterize Valence-Bond-Solid States
We propose an order parameter to characterize valence-bond-solid (VBS) states
in quantum spin chains, given by the ground-state expectation value of a
unitary operator appearing in the Lieb-Schultz-Mattis argument. We show that
the order parameter changes the sign according to the configuration of the
valence bonds. This allows us to determine the phase transition point in
between different VBS states accurately. We demonstrate this theory in the
bond-alternating Heisenberg chain and in the frustrated spin ladder.Comment: 4 pages, 1 figure, Proceedings for
Yukawa-Institute-for-Theoretical-Physics International Workshop "Order,
Disorder, and Dynamics in Quantum Spin Systems" (Nov. 2001), See also
cond-mat/011237
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