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 entropydriven phase transformations would evolve into phase transitions of the first order.

Motivated by the properties of one-dimensional lattice systems with asymmetric on-site potential, one can formulate a hypothesis of an asymmetry driven phase transformation. Characteristic feature of one-dimensional systems exhibiting asymmetry driven phase transformation is a sequence of the two phase conversions. In particular class of such systems with a triple-well potential, phase conversions of one-dimensional systems would evolve into a sequence of two phase transitions in three-dimensional models. We propose here a model of three-dimensional system exhibiting a sequence of two first order asymmetry driven phase transitions.PACS numbers: 05.70.−a, 64.60.−i, 63.70.+h MotivationIn the thermodynamic regime, one-dimensional (1D) lattice systems with degenerated vacuum, reveal the coexistence of localized and extended excitations, kinks and phonons, respectively, that is accompanied by characteristic hump developed in a specific heat [1,2]. Three--dimensional (3D) version of such a system exhibits phase transition of second order. In fact, it is one of the simplest manifestations of spontaneously broken (discrete) symmetry.It has been recently observed [3,4] that one--dimensional, multistable systems, with non-degenerated vacuum would exhibit interesting behavior. Specific heat of systems with local asymmetric, double-well or triple--well potential, may reveal quite rich, two-peak structure, possibly corresponding to two phase conversions. One can ask whether such a property of one-dimensional systems, would indicate a sequence of the phase transitions in corresponding three-dimensional systems.The aim of this paper is to give a comprehensive analysis of unconventional behaviour of specific heat of a class of one-dimensional lattice systems with triple-well potential. It is argued that large, shape-type asymmetry of these systems is manifested by "energy level crossing", associated with two-peak structure of specific heat. In this case it reflects a sequence of two phase conversions. These phase conversions would turn into phase transitions in three-dimensional version of the model. We propose here a model of a three-dimensional lattice system exhibiting a sequence of two phase transitions -they may be referred to as asymmetry driven phase transitions. The

No abstract