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Two-particle pairing and phase separation in a two-dimensional Bose-gas with one or two sorts of bosons

M. Yu. Kagan·D. V. Efremov
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Abstract

We present a phase diagram for a dilute two-dimensional Bose-gas on a lattice. For one sort of boson we consider a realistic case of the van der Waals interaction between particles with a strong hard-core repulsion $U$ and a van der Waals attractive tail $V$. For $V< 2 t $, $t$ being a hopping amplitude, the phase diagram of the system contains regions of the usual one-particle Bose-Einstein condensation (BEC). However for $V>2t$ we have total phase separation on a Mott-Hubbard Bose solid and a dilute Bose gas. For two sorts of structureless bosons described by the two band Hubbard model an s-wave pairing of the two bosons of different sort $ \neq 0$ is possible. The results we obtained should be important for different Bose systems, including submonolayers of $^4$He, excitons in semiconductors, Schwinger bosons in magnetic systems and holons in HTSC. In the HTSC case a possibility of two-holon pairing in the slave-bosons theories of superconductivity can restore a required charge $2e$ of a Cooper pair.

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M. Yu. Kagan, D. V. Efremov. 2002-04-08. Two-particle pairing and phase separation in a two-dimensional Bose-gas with one or two sorts of bosons. https://doi.org/10.1103/physrevb.65.195103

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