¹V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41, prospect Nauky, 03680 Kyiv, Ukraine E-mail: kashirina@isp.kiev.ua
²National Aviation University, 1, Kosmonavta Komarova str., 03058 Kyiv, Ukraine

Abstract. The paper is devoted to simulation of continual strong coupling condensons and bicondensons states in one-dimensional systems by using the Gaussian basis with exponentially correlated multipliers. To determine the accuracy of variational calculations, it has been shown that using the variational function consisting of a sum of 5 Gaussians reproduces the exact value of energy and wave function of the one-dimensional condenson with the accuracy of 7 and 5 significant digits, correspondingly. Analytical expressions for the effective functional of the one-dimensional bicondenson have been obtained. Variational calculations of singlet condenson ground state energy were carried out with simultaneous accounting of single-center correlations and correlations caused by a direct dependence of the bicondenson wave function on the distance between electrons. The graphical dependence of the bicondenson energy on the Coulomb repulsion parameter V C has been represented. The region of existence of bicondenson was determined as a function of electron-electron repulsion parameter V C ≤ V C * ≈ 5 . 4 . The one-center bicondenson model has been considered, and distribution of the two-electron probability density (squared wave function of bicondenson) in the region 2 ≤ V C has two maxima, the distance between which for V C = 2 is R m = 1.8567. This distribution of the probability density is associated with the low dimensionality of the system under consideration.

Keywords: polaron, 1D-bipolaron, condenson, bicondenson, low-dimensional systems, electron-phonon interaction.

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