Recent Publications

Tchavdar Todorov

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  1. Title: Correlated electron-ion dynamics in metallic systems

    Author(s): Horsfield A.P., Finnis M., Foulkes M., LePage J., Mason D., Race C., Sutton A.P., Bowler D.R., Fisher A.J., Miranda R., Stella L., Stoneham A.M., Dundas D., McEniry E., Todorov T.N., Sanchez C.G.,

    Computational Materials Science, 44, No. 1, pp. 16-20 (November 2008)

    doi: 10.1016/j.commatsci.2008.01.055

    In this paper we briefly discuss the problem of simulating non-adiabatic processes in systems that are usefully modelled using molecular dynamics. In particular we address the problems associated with metals, and describe two methods that can be applied: the Ehrenfest approximation and correlated electron-ion dynamics (CEID). The Ehrenfest approximation is used to successfully describe the friction force experienced by an energetic particle passing through a crystal, but is unable to describe the heating of a wire by an electric current. CEID restores the proper heating. (C) 2008 Elsevier B.V. All rights reserved.

  2. Title: Newtonian origin of the spin motive force in ferromagnetic atomic wires

    Author(s): Stamenova M., Todorov T.N., Sanvito S.,

    Physical Review B, 77, No. 5 (2008)

    doi: 10.1103/PhysRevB.77.054439

    We demonstrate numerically the existence of a spin-motive force acting on spin carriers when moving in a time and space dependent internal field. This is the case for electrons in a one-dimensional wire with a precessing domain wall. The effect can be explained solely by adiabatic dynamics and is shown to exist for both classical and quantum systems.

  3. Title: Inelastic quantum transport in nanostructures: The self-consistent Born approximation and correlated electron-ion dynamics

    Author(s): McEniry E.J., Frederiksen T., Todorov T.N., Dundas D., Horsfield A.P.,

    Physical Review B, 78, No. 3 (2008)

    doi: 10.1103/PhysRevB.78.035446

    A dynamical method for inelastic transport simulations in nanostructures is compared to a steady-state method based on nonequilibrium Green's functions. A simplified form of the dynamical method produces, in the steady state in the weak-coupling limit, effective self-energies analogous to those in the Born approximation due to electron-phonon coupling. The two methods are then compared numerically on a resonant system consisting of a linear trimer weakly embedded between metal electrodes. This system exhibits an enhanced heating at high biases and long phonon equilibration times. Despite the differences in their formulation, the static and dynamical methods capture local current-induced heating and inelastic corrections to the current with good agreement over a wide range of conditions, except in the limit of very high vibrational excitations where differences begin to emerge.