35 research outputs found
Dynamical phase diagram of the dc-driven underdamped Frenkel-Kontorova chain
Multistep dynamical phase transition from the locked to the running state of
atoms in response to a dc external force is studied by MD simulations of the
generalized Frenkel-Kontorova model in the underdamped limit. We show that the
hierarchy of transition recently reported [Braun et al, Phys. Rev. Lett. 78,
1295 (1997)] strongly depends on the value of the friction constant. A simple
phenomenological explanation for the friction dependence of the various
critical forces separating intermediate regimes is given.Comment: 12 Revtex Pages, 4 EPS figure
Role of bulk and surface phonons in the decay of metal surface states
We present a comprehensive theoretical investigation of the electron-phonon
contribution to the lifetime broadening of the surface states on Cu(111) and
Ag(111), in comparison with high-resolution photoemission results. The
calculations, including electron and phonon states of the bulk and the surface,
resolve the relative importance of the Rayleigh mode, being dominant for the
lifetime at small hole binding energies. Including the electron-electron
interaction, the theoretical results are in excellent agreement with the
measured binding energy and temperature dependent lifetime broadening.Comment: 4 pages, 3 figure
Surface Screening Charge and Effective Charge
The charge on an atom at a metallic surface in an electric field is defined
as the field-derivative of the force on the atom, and this is consistent with
definitions of effective charge and screening charge. This charge can be found
from the shift in the potential outside the surface when the atoms are moved.
This is used to study forces and screening on surface atoms of Ag(001)
c -- Xe as a function of external field. It is found that at low
positive (outward) fields, the Xe with a negative effective charge of -0.093
is pushed into the surface. At a field of 2.3 V \AA the charge
changes sign, and for fields greater than 4.1 V \AA the Xe experiences
an outward force. Field desorption and the Eigler switch are discussed in terms
of these results.Comment: 4 pages, 1 figure, RevTex (accepted by PRL
Phonons and solitons in the "thermal" sine-Gordon system
Standard methods of stochastic processes are used to study the coupling of the sine-Gordon system with a heat reservoir. As a result we find thermal phonons with an average energy of kB T per mode. The translational mode (zero mode) is found to carry an average energy of 1/2kBT. This last value is just the energy in the Brownian motion of a thermal soliton. These results are in agreement with those obtained by the use of a statistical-mechanical description of a dilute soliton gas. Connection of the above results with Josephson junctions and the extension of the analysis to more general equations is also discussed