Recent Publications

Tchavdar Todorov

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  1. Title: Magnetomechanical interplay in spin-polarized point contacts

    Author(s): Stamenova M., Sahoo S., Sanchez C.G., Todorov T.N., Sanvito S.

    Physical Review B, 73, No. 9, Art. No. 094439 (MAR 2006)

    doi: 10.1103/PhysRevB.73.094439

    We investigate the interplay between magnetic and structural dynamics in ferromagnetic atomic point contacts. In particular, we look at the effect of the atomic relaxation on the energy barrier for magnetic domain wall migration and, reversely, at the effect of the magnetic state on the mechanical forces and structural relaxation. We observe changes of the barrier height due to the atomic relaxation up to 200%, suggesting a very strong coupling between the structural and the magnetic degrees of freedom. The reverse interplay is weak; i.e., the magnetic state has little effect on the structural relaxation at equilibrium or under nonequilibrium, current-carrying conditions.

  2. Title: Molecular conduction: Do time-dependent simulations tell you more than the Landauer approach?

    Author(s): Sanchez C.G., Stamenova M., Sanvito S., Bowler D.R., Horsfield A.P., Todorov T.N.

    Journal Of Chemical Physics, 124, No. 21, Art. No. 214708 (JUN 7 2006)

    doi: 10.1063/1.2202329

    A dynamical method for simulating steady-state conduction in atomic and molecular wires is presented which is both computationally and conceptually simple. The method is tested by calculating the current-voltage spectrum of a simple diatomic molecular junction, for which the static Landauer approach produces multiple steady-state solutions. The dynamical method quantitatively reproduces the static results and provides information on the stability of the different solutions. (c) 2006 American Institute of Physics.

  3. Title: The transfer of energy between electrons and ions in solids

    Author(s): Horsfield A.P., Bowler D.R., Ness H., Sanchez C.G., Todorov T.N., Fisher A.J.

    Reports On Progress In Physics, 69, No. 4, pp. 1195-1234 (APR 2006)

    doi: 10.1088/0034-4885/69/4/R05

    In this review we consider those processes in condensed matter that involve the irreversible flow of energy between electrons and nuclei that follows from a system being taken out of equilibrium. We survey some of the more important experimental phenomena associated with these processes, followed by a number of theoretical techniques for studying them. The techniques considered are those that can be applied to systems containing many nonequivalent atoms. They include both perturbative approaches (Fermi's Golden Rule and non-equilibrium Green's functions) and molecular dynamics based (the Ehrenfest approximation, surface hopping, semi-classical Gaussian wavefunction methods and correlated electron-ion dynamics). These methods are described and characterized, with indications of their relative merits.