Alexey Menushenkov

Name: Alexey Menushenkov
Title: Prof.
Institution: Moscow State Engineering Physics Institute
Address: Kashirskoe shosse 31
City, ZIP code: Moscow 115409
Country: Russia
E-mail: menushen@htsc.mephi.ru
Interests: Thermal vibrations and anharmonicity, Superconductors, Materials science
Keywords: high temperature superconductors, perovskite-like structures,
Ba(K)BiO3, BaBi(Pb)O3, Nd(Ce)CuO, YBaCuO,
anharmonicity of oxygen vibrations, double-well potential,
local crystal and local electronic structures,
symmetry of free electronic states, valency states of Bi
and Cu, Debye-Waller factor temperature dependence,
rotation (tilting) phonon modes, breathing phonon modes
Brief description of the work:

Firstly applied EXAFS for study of local structure of superconucting
oxide (BaBi(Pb)O) in 1984. The influence of oxygen contain and
doping (K or Pb) concentration on the local electronic and local
crystal structutes of doped BaBiO3 was investigated by XANES and EXAFS
spectroscopy. The Bi-valence state was explained.
It was shown that oxygen ions move in double-well potential and their
oscillations are correlated with charge carrier movement. Observed
breathing-like oxygen vibration in double-well potential with large
amplitude and low frequency causes the strong electron-phonon
coupling and high Tc values in doped BaBiO3. Based on the experimental
data, the model of relationship of electronic and local crystal
structures is proposed that is in a good agreement with the results
of transport measurements, inelastic neutron and electron
scattering, Raman scattering, and photoemission spectroscopy.
In the framework of the model the possible reasons of
superconductivity in perovskite-like oxides are discussed.
The influence of He++ ion irradiation on the local crystal and local
electronic structures of Nd(Ce)CuO and YBaCuO was studied. The
symmetry of free electronic states was explained.