Successive phase transitions and Kink solutions in phi8, phi10 and phi12 field theories

Abstract

We obtain exact solutions for kinks in 8,10and 12field theories with degenerate minima, which can describe a second-order phase transition followed by a first-order one, a succession of two first-order phase transitions and a second-order phase transition followed by two first-order phase transitions, respectively. Such phase transitions are known to occur in ferroelastic and ferroelectric crystals and in meson physics. In particular, we find that the higher-order field theories have kink solutions with algebraically decaying tails and also asymmetric cases with mixed exponential-algebraic tail decay, unlike the lower-order 4and 6theories. Additionally, we construct distinct kinks with equal energies in all three field theories considered, and we show the coexistence of up to three distinct kinks (for a 12potential with six degenerate minima). We also summarize phonon dispersion relations for these systems, showing that the higher-order field theories have specific cases in which only nonlinear phonons are allowed. For the field theory, which is a quasiexactly solvable model akin to we are also able to obtain three analytical solutions for the classical free energy as well as the probability distribution function in the thermodynamic limit.