Light Bipolarons Stabilized by Peierls Electron-Phonon Coupling

It is widely accepted that phonon-mediated high-temperature superconductivity is impossible at ambient pressure, because of the very large effective masses of polarons or bipolarons at strong electron-phonon coupling. Here we challenge this belief by showing that strongly bound yet very light bipola...

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Bibliographic Details
Published in:Physical review letters 2018-12, Vol.121 (24), p.247001-247001, Article 247001
Main Authors: Sous, John, Chakraborty, Monodeep, Krems, Roman V, Berciu, Mona
Format: Article
Language:English
Subjects:
Carrier density
Computer simulation
Coupling
High temperature
Pressure
Superconductivity
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Summary:It is widely accepted that phonon-mediated high-temperature superconductivity is impossible at ambient pressure, because of the very large effective masses of polarons or bipolarons at strong electron-phonon coupling. Here we challenge this belief by showing that strongly bound yet very light bipolarons appear for strong Peierls coupling. These bipolarons also exhibit many other unconventional properties; e.g., at strong coupling there are two low-energy bipolaron bands that are stable against strong Coulomb repulsion. Using numerical simulations and analytical arguments, we show that these properties result from the specific form of the phonon-mediated interaction, which is of "pair hopping" instead of regular density-density type. This unusual effective interaction is bound to have nontrivial consequences for the superconducting state expected to arise at finite carrier concentrations and should favor a large critical temperature.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.121.247001