paper

A Renormalization Group Study of Helimagnets in D=2+EPSILON Dimensions

arXiv:cond-mat/9304049 · doi:10.1016/0550-3213(93)90376-Z

Abstract

We study a non linear sigma model describing the phase transition of N-components helimagnets up to two loop order in dimensions. It is shown that a stable fixed point exists as soon as is greater than 3 (or equal). In the N=3 case, the symmetry of the system is dynamically enlarged at the fixed point to O(4) We show that the order parameter for Heisenberg helimagnets involves a tensor representation of . We show that for large and in the neighborhood of two dimensions this nonlinear sigma model describes the same critical theory as the Landau-Ginzburg linear theory. We deduce that there exists a dividing line in the plane separating a first-order region containing the Heisenberg point at and a second-order region containing the whole axis. We conclude that the phase transition of Heisenberg helimagnets in dimension 3 is either first order or second order with exponents involving a tensor representation or tricritical.

25 pages and 1 figure not included, LateX, Saclay preprint SPhT/93-044

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