Continuum Elastic Theory for Dynamics of Surfaces and Interfaces

Continuum elastic theory remains a valuable tool of modern condensed matter 
physics. In this talk I will present three applications of elastic theory to 
surface physics problems that form the core of my dissertation research:

(i) Step induced phonons at vicinal surfaces. 
Elastic theory is used to obtain the vibrational density of states at a 
stepped surface. Step induced phonons appear as peaks in the surface density 
of states. For Ni(977) surface I compare the predictions of the elastic 
model with recently reported experimental data obtained by inelastic He atom 
scattering.  

(ii) Adsorbate vibrational relaxation.
Elastic theory is used to study damping of low-frequency adsorbate vibrations
via resonant coupling to the substrate phonons. Our theory provides a general
expression for the vibrational damping rate which can be applied to widely
varying coverages and arbitrary overlayer structures. The damping rates
predicted by our theory for CO on Cu(100) are in excellent quantitative
agreement with available experimental data.

(iii) Guided elastic waves in thin films. 
Elastic theory is used to obtain the vibrational density of states
at the surface of a thin film of one anisotropic solid an on top of the other. 
Guided elastic waves appear as peaks in the surface density of states.
For a GaN film on a sapphire substrate I obtained dispersion curves of two 
families of the guided waves: Love waves (shear horizontal polarization) and 
Sezawa and Kanai waves (saggital polarization).