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Phys. Rev. Lett. 89, 247201 (2002) [4 pages]

Striped Phase in a Quantum XY Model with Ring Exchange

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A. W. Sandvik1,2, S. Daul3,*, R. R. P. Singh4, and D. J. Scalapino2
1Department of Physics, Åbo Akademi University, Porthansgatan 3, FIN-20500 Turku, Finland
2Department of Physics, University of California, Santa Barbara, California 93106
3Institute of Theoretical Physics, University of California, Santa Barbara, California 93106
4Department of Physics, University of California, Davis, California 95616

Received 13 May 2002; published 21 November 2002

We present quantum Monte Carlo results for a square-lattice S=1/2 XY model with a standard nearest-neighbor coupling J and a four-spin ring exchange term K. Increasing K/J, we find that the ground state spin stiffness vanishes at a critical point at which a spin gap opens and a striped bond-plaquette order emerges. At still higher K/J, this phase becomes unstable and the system develops a staggered magnetization. We discuss the quantum phase transitions between these phases.

© 2002 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.89.247201
DOI:
10.1103/PhysRevLett.89.247201
PACS:
75.10.–b, 05.30.–d, 75.40.Mg

*Present address: Swiss Re, Mythenquai 50/60, 8022 Zürich, Switzerland.

 
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