Light bipolarons in a system of electrons coupled to dispersive optical phonons

Kovač, Klemen (author), Bonča, Janez (author)

We investigate the ground-state properties of the bipolaron coupled to quantum dispersive optical phonons in the one-dimensional Holstein-Hubbard model. We concentrate on the interplay between the phonon dispersion and the Coulomb repulsion and their mutual effect on the bipolaron effective mass, the binding energy, and the phase diagram. Most surprisingly, the sign of the curvature of the optical phonon dispersion plays a decisive role in the bipolaron binding energy in the presence of the Coulomb repulsion $U$. In particular, when the sign of the phonon dispersion curvature matches the sign of the electron dispersion curvature, the bipolaron remains bound in the strong-coupling limit even when $U \to \infty$ and the binding emanates from the exchange of phonons between two electrons residing on adjacent sites. At moderate electron-phonon coupling a light bipolaron exists up to large values of $U$. Finally, an intuitive explanation of the role of the phonon dispersion on the bipolaron binding energy is derived using the strong-coupling limit where the binding emanates from the exchange of phonons between two electrons residing on adjacent sites which leads to enhanced stability of bipolarons at elevated Coulomb repulsion.

• Language: English
• Keywords: bipolaronic systems, phonons, phononic dispersion, electron-phonon interaction
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication version: Author Accepted Manuscript
• Publication date: 12.02.2024
• Year: 2024
• Number of pages: Str. 064304-1-064304-8
• Numbering: Vol. 109, iss. 6, [article no.] 064304
• PID: 20.500.12556/RUL-154891
• UDC: 53
• ISSN on article: 2469-9969
• DOI: 10.1103/PhysRevB.109.064304
• COBISS.SI-ID: 185285123
• Publication date in RUL: 07.03.2024

Record is a part of a journal

• Title: Physical review
• Shortened title: Phys. rev. B.
• Publisher: American Physical Society
• ISSN: 2469-9969
• COBISS.SI-ID: 3042148

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0044
• Name: Teorija trdnih snovi in statistična fizika