Condensed Matter Physics, 2012, vol. 15, No. 4, p. 43001:1-10
DOI:10.5488/CMP.15.43001           arXiv:1206.3853

Title: Marginal dimensions for multicritical phase transitions
Author(s):
  M. Dudka (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine) ,
  R. Folk (Institut für Theoretische Physik, Johannes Kepler Universität Linz, A-4040, Linz, Austria) ,
  Yu. Holovatch (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine) ,
  G. Moser (Fachbereich für Materialforschung und Physik, Univerität Salzburg, A-5020 Salzburg, Austria)

The field-theoretical model describing multicritical phenomena with two coupled order parameters with n || and n components and of O(n||) ⊕ O(n) symmetry is considered. Conditions for realization of different types of multicritical behaviour are studied within the field-theoretical renormalization group approach. Surfaces separating stability regions for certain types of multicritical behaviour in parametric space of order parameter dimensions and space dimension d are calculated using the two-loop renormalization group functions. Series for the order parameter marginal dimensions that control the crossover between different universality classes are extracted up to the fourth order in ϵ = 4-d and to the fifth order in a pseudo-ϵ parameter using the known high-order perturbative expansions for isotropic and cubic models. Special attention is paid to a particular case of O(1)O(2) symmetric model relevant for description of anisotropic antiferromagnets in an external magnetic field.

Key words: multicritical phenomena, marginal dimensions, renormalization group
PACS: 05.50.+q, 64.60.ae


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