Light Bipolarons Stabilized by Peierls Electron-Phonon Coupling

Abstract

It is widely accepted that phonon-mediated high-temperature superconductivity is impossible at ambient pressure, because of the very large effective masses of polarons/bipolarons at strong electron-phonon coupling. Here we challenge this belief by showing that strongly bound yet very light bipolarons appear for strong Peierls/Su-Schrieffer-Heeger 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 phononmediated interaction, which is of "pair-hopping" instead of regular density-density type. This unusual effective interaction is bound to have non-trivial consequences for the superconducting state expected to arise at finite carrier concentrations, and should favor a large critical temperature.

Pump-probe spectroscopy of Bose polarons: Dynamical formation and coherence

“…Understanding the physics of quasiparticles is important beyond cold atom settings in semiconducting [65] and superconducting devices [66]. Additionally, interactions among quasiparticles in liquid helium mixtures [67,68] and cuprates [69,70] are considered to be responsible for conventional and high-T c superconductivity [71][72][73][74][75][76][77]. Here we consider a Bose-Einstein condensate (BEC) with one or two impurities of either bosonic or fermionic nature immersed into it and track the emergent Bose polaron formation [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] with a PPS radiofrequency protocol analogous to the one used in the experiment of Ref.…”

Quantum Monte Carlo study of lattice polarons in the two-dimensional three-orbital Su–Schrieffer–Heeger model

“…Lattice dimerization in one-dimension was initially described by the Su-Schrieffer-Heeger (SSH) model 1 , in which the atomic motion modulates the overlap integrals between neighboring atoms. Recently, SSH-like models have attracted further attention due to the fact that they can produce highly mobile polarons with light effective masses 9 , generate robust phonon-mediated pairing 10 , and even stabilize and control the location of a type-II Dirac point 11 . SSH interactions are also believed to be dominant mechanism for electron-phonon (e-ph) interactions in materials like the high-T c cuprates 12,13 .…”

Superconductivity due to cooperation of electron-electron and electron-phonon interactions at quarter filling

“…These include a nearest neighbor repulsion for parallel spins, on-site pair terms (which will be suppressed by U ), and pair hopping of nearest-neighbor singlet pairs. Recent work has shown that this pair hopping interaction leads to strongly bound bipolarons with light effective masses that are stable against strong e-e interactions [30]. This suggests the possibility of e-p mediated SC in the presence of strong e-e interactions at finite carrier densities.…”