Kinks and periodons at aT=0 first-order phase transition point in one-dimensional anharmonic lattices

Abstract

One-dimensional lattices with harmonic coupling between neighboring lattice sites and an on-site anharmonic potential V(φ)=Aφ2n+2 + φn+2 + Cφ2 + D are examined in the displacive limit. Kink solutions, interpolating between the coexistent phases ϕ=0 and ϕ=±(C/A)1/2n at theT=0 first-order phase transition pointB 2=4AC,A, C>0,B<0,D=0 are found in simple analytic form and their dependence on the degree of anharmonicity (n=2, 4, 6, ...) is discussed. It is shown that, at the phase transition point, the kinks are accompanied by a continuous spectrum of periodic nonlinear excitations (“periodons”) having finite energy density.