First-order transition between magnetic order and valence bond order in a 2D frustrated Heisenberg model
Physique Quantique, Université Paul Sabatier - 31062 Toulouse, France
Accepted: 28 February 1996
We study the competition between magnetic order and valence bond order in a two-dimensional (2D) frustrated Heisenberg model introduced some time ago by Shastry and Sutherland (Physica B, 108 (1981) 1069) for which a configuration of dimers is known to be the ground state in a certain range of parameters. Using exact diagonalization of small clusters, linear spin wave theory and Schwinger boson mean-field theory, we argue that the transition between the two types of order is first order, and that it takes place inside the domain where magnetic long-range order is stable with respect to quantum fluctuations.
PACS: 75.10.Jm – Quantized spin models / 75.30.Ds – Spin waves / 75.30.Kz – Magnetic phase boundaries (including magnetic transitions, metamag ne tism, etc.)
© EDP Sciences, 1996