ABSTRACT
Thermodynamic properties of one-dimensional lattice models exhibiting entropy-driven phase transformations are discussed in quantum and classical regimes. Motivated by the multistability of compounds exhibiting photoinduced phase transitions, we consider systems with asymmetric, double, and triple well on-site potential. One finds that among a variety of regimes, quantum versus classical, discrete versus continuum, a key feature is asymmetry distinguished as a "shift" type and "shape" type in limiting cases. The behavior of the specific heat indicates one phase transformation in a "shift" type and a sequence of two phase transformations in "shape"-type systems. Future analysis in higher dimensions should allow us to identify which of these entropy-driven phase transformations would evolve into phase transitions of the first order.
ABSTRACT
Classical thermodynamics of the (1+1)-dimensional asymmetric double sinh-Gordon system is investigated. The pseudo-Schrödinger equation resulting from the transfer integral method is solved numerically and within the semiclassical approximation; the exact results are also given at several temperatures. It is found that the specific heat exhibits a characteristic hump resembling a similar one observed in the systems with a symmetric potential; in some structures, extremely narrow and extremely high peak is developed. The interpretation for this behavior is given.
ABSTRACT
It is shown that the nontopological (bell-shaped) solitary waves in the asymmetric straight phi(4) model are unstable and correspond to saddle points of the potential energy of the continuous system. Their lifetime is estimated. In the discrete model, the potential energy landscape becomes rough: bell-shaped configurations may become stable. The potential energy function is analyzed around the bell-shaped configurations. A dynamical scenario for the decay of the metastable state in a discrete system, related to spontaneous energy localization, is shown.
