https://doi.org/10.15407/spqeo5.03.235
Semiconductor Physics, Quantum
Electronics & Optoelectronics. 2002. V. 5, N 3. P. 235-242.
PACS: 71.38, 73.20.D, 74.80.D
Investigation of electron correlation effect on energy spectrum of two-electron systems in crystals with strong electron-phonon coupling
Institute of Semiconductor Physics, NAS
of Ukraine, 45 prospect Nauky, 03028 Kyiv, Ukraine
E-mail: kashirin@class.semicond.kiev.ua
*Institute of Mathematical Problems of Biology, RAS, 142290 Pushchino,
Russia
E-mail: lak@impb.psn.ru
Abstract.The
influence of electron correlations (direct dependence of electronic wave
function on distance between electrons) on energy spectra of two-electron
systems (D-,
F ' , F2-centers
and bipolarons) in polar crystals with strong electron-phonon interaction
is investigated. Bipolaron is chosen as the simplest model of two-electron
system in the crystal. Bipolaron energy is calculated for various distances
between the centers of polarization wells of two polarons with accounting
the electron correlations. A singlet bipolaron is stable at rather high
energy of ion binding 
0,143
. The unique
energy minimum corresponds to a one-center bipolaron (an analog of a helium
atom). The bipolaron binding energy constitutes up to 25.8% of a double
polaron energy at 
.
A triplet bipolaron (an analog of orthohelium) is energetically disadvantageous.
The one-center configuration of a triplet bipolaron corresponds to a maximum
on the distance dependence of the total energy 
.
The exchange interaction between polarons has antiferromagnetic character.
A prediction is made about a possibility of the Wigner crystallization
of a polaron gas, which occurs with antiferromagnetic ordering in the
polaron system. The examples of energy calculations with accounting the
electron correlations of exchanged-coupled pairs, D-
and F '-centers in polar
crystals are also given.
Keywords: bipolaron,
Frölich Hamiltonian, electron-phonon interaction, electron correlations,
superconductivity, high-temperature superconductivity
Paper received 12.04.02; revised manuscript
received 02.09.02; accepted for publication 10.12.02.
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