Nature of the vibron self-trapped states in hydrogen-bonded macromolecular chains

Abstract

We study the influence of temperature and the values of basic energy parameters on the character of vibron self-trapped states in quasi-one-dimensional hydrogen-bonded molecular chains. Investigations have been carried out within the one-dimensional Holstein molecular crystal model employing the variational extension of the Lang-Firsov unitary transformation. It was found that, in the low-temperature regime, only partially dressed small-polaron states may exist. With the rise of temperature, the system enters the metastability region, where partially dressed (light and mobile) and fully dressed (heavy and practically immobile) small-polaron states may exist simultaneously.

Structural levels of deformation and failure of heat-resistant 12Cr1MoV steel modified by vacuum arc treatment by Zr+ ion beam

“…In order to find the most favorable vibron state, we follow the procedure which is described in [3]. Shortly, we reached partially dressed polaron picture with use of of the modified Lang -Firsov unitary transformation (MLFUT) for the Hamiltonian (1).…”

“…From technical viewpoint, the method based on using of the MLFUT is variational method where the variational parameters determine the participation of the each phonon mode to the quasiparticle dressing. Doing so, we consider the variational method with single variational parameter, 1 0    [3,10], which is especially useful to derive the results due to its simplicity. This parameter may be used as a measure of the degree of the vibron dressing.…”

“…The further calculations should be made in terms of two independent dimensionless parameters: adiabatic parameter B , determining the character of the lattice deformation engaged in the polaron formation and coupling constant S [2,3]. In the case when quasiparticle interacts with non dispersional optical phonon modes, they become: For the same values of the system parameters, relative diffusivity (i.e.…”

“…All these processes involve protein molecules as mediators of the long distance energy transfer. According to recent research [2,3,4], vibron self-trapping (ST) in protein macromolecules, and other biological macromolecular chains (MCs), will result in creation of partially dressed rather than fully dressed small polaron state (for solitonic nature of energy ST when the potential well may induced by local distortion of the molecular crystals, see e.g. [5]).…”

“…As a consequence, the properties of ST vibron state may be quite different compared with the properties of the bare vibron excitation or fully dressed small polaron state. In fact, it was found that for the partially dressed vibrons there exist such values of the system parameters (critical values) for which the quasiparticle state abruptly changes from weakly dressed to heavy dressed, practically localized vibron state [2,3,6,7]. It was also found that the critical values of the system parameters are temperature dependent, and for some biological structures may belong to room temperature interval.…”