Semiconductor Physics, Quantum Electronics & Optoelectronics, 5 (3), P. 235-242 (2002)
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


N.I.Kashirina, V.D.Lakhno*, V.V.Sychyov*


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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