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Atomic scale investigation of low-energy excitation at surface and interface by inelastic electron tunneling spectroscopy

Monday, March 05, 2018 - 12:00
Donostia International Physics Center
Emi Minamitani (University of Tokyo, Japan)
Source Name: 

electron tunneling spectroscopy (IETS) combined with scanning tunneling
microscopy (STM) allows us to acquire vibrational signals at surfaces. In
STM-IETS, a tunneling electron from the STM tip excites vibrations whenever the
energy of tunneling electron exceeds the vibrational energies. This opens up an
inelastic channel in parallel with the elastic one and gives rise to an
increase/decrease of the conductivity in the STM junction. As a consequence, a
pair of peak and dip shows up at the bias voltages with respect to the Fermi
level corresponding to the energy of vibrational energy. Until recently, the
application of STM-IETS was limited to the localized vibration of single atoms
and molecules adsorbed on surfaces. In principle, STM-IETS should be capable of
detecting the collective lattice dynamics, i.e., phonons. In this talk, I will
introduce the example STM-IETS measurement for surface
and interface phonons and provides the theoretical analysis behind them. The
surface phonon on Cu(110) and interface phonons relevant of graphene on SiC
substrate are good examples. In the former part, I will provide theoretical
formalism about the electron-phonon coupling upon the electron tunneling based
on a simple model Hamiltonian. In the latter case, we discuss the spatial
dependence of the IETS spectrum induced by the excitation of the interface
phonons based on the ab initio calculations.  

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