Many-body interaction induced exotic phenomena at surface: molecular Kondo effect and inelastic process in laser-photoemission
CFM Seminars
- Speaker
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Emi Minamitani (Department of Materials Engineering, The University of Tokyo)
- When
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2015/09/11
14:00 - Place
- Donostia International Physics Center (DIPC)
- Add to calendar
-
iCal
**Many-body interaction induced exotic phenomena at surface: molecular Kondo
effect and inelastic process in laser-photoemission**
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Emi Minamitani
_Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo
Bunkyo-ku Tokyo, Japan_
Recent development of the theoretical/experimental techniques enables us to
explore low-energy excitations induced by many-body interaction at surface. In
this talk, I will introduce two of my theoretical studies in this field: 1)
Kondo effect in molecules at surfaces, 2) inelastic process appears in laser-
photoemission spectroscopy.
The Kondo effect [1] is one of the intriguing phenomena arising from the
interaction between localized magnetic moments and conduction electrons. The
Kondo singlet state resulting from the Kondo effect changes the magnetic state
and the conductivity drastically, which yields a sharp peak or dip structure
at the Fermi level in scanning tunneling spectrum (STS). Recently, the
observations of the Kondo effect by STS have been reported in various
phthalocyanine and porphyrin molecules on metal surfaces [2]. To elucidate the
mechanism of molecular Kondo effects, I have carried out theoretical studies
by density functional theory (DFT) and numerical renormalization group (NRG)
in collaboration with experimental groups. In this talk, I will introduce the
results on Mn-phthalocyanine (MnPc) on Pb(111), in which the π-d interaction
plays a crucial role to mediate indirect Kondo screening and form a spatially
extended Kondo state [3].
Laser-photoemission spectroscopy (LPES) at metal surface with low-energy
photons of ~ 5eV can probe phonons at surfaces through the photoelectron-
phonon interaction. The inelastic interaction produces a spectral component
whose shape is a replica of the elastic one downshifted by the vibrational
energy relative to the Fermi level. Such inelastic LPES signals have been
observed in CO/Cu(001) [4] and clean Cu(110) surface [5], but the mechanism of
the phonon excitation during the photoemission process remained unanswered. I
investigated this inelastic excitation process on Cu(110) using ab-initio
calculations including electron-phonon coupling calculation based on the
density functional perturbation theory. As a result, I found strong wavevector
and energy dependence in the electron-phonon coupling, which causes selective
excitation of the subsurface phonon by photoelectron [6].
I thank Prof. N. Takagi, Prof. M. Kawai, Dr. N. Tsukahara, Dr. R. Arafune, Dr.
Y. Kim, Dr. Y. Fu, Prof. Q. K. Xue, and Prof. S. Watanabe for discussions and
collaboration in the works presented in