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New Ordered Phases in a Class of Generalized XY Models Fabio C. Poderoso, Jeferson J. Arenzon, and Yan Levin
 

Summary: New Ordered Phases in a Class of Generalized XY Models
Fa´bio C. Poderoso, Jeferson J. Arenzon, and Yan Levin
Instituto de Fi´sica, Universidade Federal do Rio Grande do Sul, CP 15051, 91501-970 Porto Alegre RS, Brazil
(Received 6 August 2010; revised manuscript received 12 December 2010; published 10 February 2011)
It is well known that the 2D XY model exhibits an unusual infinite order phase transition belonging to
the Kosterlitz-Thouless (KT) universality class. Introduction of a nematic coupling into the XY
Hamiltonian leads to an additional phase transition in the Ising universality class [D. H. Lee and G.
Grinstein, Phys. Rev. Lett. 55, 541 (1985)]. Using a combination of extensive Monte Carlo simulations
and finite size scaling, we show that the higher order harmonics lead to a qualitatively different phase
diagram, with additional ordered phases originating from the competition between the ferromagnetic and
pseudonematic couplings. The new phase transitions belong to the 2D Potts, Ising, or KT universality
classes.
DOI: 10.1103/PhysRevLett.106.067202 PACS numbers: 75.10.Àb, 64.70.mf, 75.30.Kz, 75.40.Mg
The low-temperature behavior of two dimensional (2D)
systems with continuous symmetries is controlled by to-
pological defects, such as vortices and domain walls.
Although massless Goldstone excitations, such as spin
waves, destroy the long-range order of these systems, a
pseudo-long-range order with algebraically decaying cor-
relation functions still remains possible. At low tempera-

  

Source: Arenzon, Jeferson J. - Instituto de Física, Universidade Federal do Rio Grande do Sul
Levin, Yan - Instituto de Física, Universidade Federal do Rio Grande do Sul

 

Collections: Physics