Open AccessA New Universality at a First-Order Phase Transition: The Spin-flop Transition in an Anisotropic Heisenberg Antiferromagnet
Author(s) -
Jiahao Xu,
Shan-Ho Tsai,
D. P. Landau,
Kurt Binder
Publication year - 2020
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1483/1/012004
Subject(s) - physics , universality (dynamical systems) , phase transition , antiferromagnetism , degenerate energy levels , renormalization group , monte carlo method , anisotropy , heisenberg model , statistical physics , degeneracy (biology) , condensed matter physics , quantum mechanics , mathematics , bioinformatics , statistics , biology
A great triumph of statistical physics in the latter part of the 20th century was the understanding of critical behavior and universality at second-order phase transitions. In contrast, first-order transitions were believed to have no common features. However, we argue that the classic, first-order “spin-flop” transition (between the antiferromagnetic and the rotationally degenerate, canted state) in an anisotropic antiferromagnet in a magnetic field exhibits a new kind of universality. We present a finite-size scaling theory for a first-order phase transition where a continuous symmetry is broken using an approximation of Gaussian probability distributions with a phenomenological degeneracy factor “ q ” included, where “ q ” characterizes the relative degeneracy of the ordered phases. Predictions are compared with high resolution Monte Carlo simulations of the three-dimensional, XXZ Heisenberg antiferromagnet in a field to study the finite-size behavior for L×L×L simple cubic lattices. The field dependence of all moments of the order parameters exhibit universal intersections at the spin-flop transition. Our Monte Carlo data agree with theoretical predictions for asymptotic large L behavior. Our theory yields q = π , and we present numerical evidence that is compatible with this prediction. The agreement between the theory and simulation implies a heretofore unknown universality.