Session of Monday, March 6, 2017 from 18-19 hours at at IMUS: Seminario I. Avda. Reina Mercedes s/n. 41012 Sevilla (in front of Luca de Tena Street).

Dr. Larissa Brizhik

Orcid:0000-0002-5668-7740 , Prigogine Gold Medal 2011, former Head of the Department of Condensed Matter Physics at the Bogolyubov Institute for Theoretical Physics, Kiev:, Ukraine.

Soliton assisted hyperconductivity of low-dimensional systems: role of electron-phonon coupling and lattice anharmonicity (pdf slides)

1. The soliton mechanism of hyperconductivity of low-dimensional systems is discussed. Solitons in such systems are formed due to binding of electrons with phonons of the lattice.
2.     It is shown that at sufficient levels of system doping, binding of two electrons with opposite spins in a bound localized state called bisoliton, takes place in harmonic lattices. Bisolitons in harmonic lattices can propagate with velocity below the velocity of the sound in the system. Similarly, binding of electrons in singlet spin state, called bisolectron, takes place in anharmonic lattices. It is shown that the account of the lattice anharmonicity leads to the stabilization of bisolectron dynamics: bisolectrons are dynamically stable up to the sound velocity. This is demonstrated for lattices with cubic and quartic anharmonicities. The bisolectrons have finite values of energy and momentum in the whole interval of the velocities up to the sound velocity. Also analytical solutions for supersonic bisolectrons are found at certain values of the system parameters.
3.     The bisolectron binding energy and critical value of the Coulomb repulsion at which the bisolectron becomes unstable and decays into two independent solitons, are calculated. The analytical results are in a good agreement with the results of numerical simulations in a broad interval of the parameter values.
4.     Such solitons, bisolitons and bisolectrons correspond to the ground state of the electron-phonon system at intermediate values of the electron-lattice coupling, such as polydiacetylene, macromolecules, conducting polymers, etc. Such nonlinear charge carriers provide coherent transport of electrons, stable against temperature up to some critical value and are stable against lattice disorder. In lattices with strong enough anharmonicity bisolectrons can propagate with high velocity. Thus, such a nonlinear mechanism can provide hyperconductivity of low-dimensional systems (quasi-one-dimensional and two-dimensional).
   

Organized by JFR Archilla and the Nonlinear Physics Group (GFNL) of the University of Sevilla