title: Sharp transition for single polarons in the one-dimensional Su-Schrieffer-Heeger model.
abstract: We study a single polaron in the Su-Schrieffer-Heeger (SSH) model using four different techniques (three numerical and one analytical). Polarons show a smooth crossover from weak to strong coupling, as a function of the electron-phonon coupling strength λ, in all models where this coupling depends only on phonon momentum q. In the SSH model the coupling also depends on the electron momentum k; we find it has a sharp transition, at a critical coupling strength λ(c), between states with zero and nonzero momentum of the ground state. All other properties of the polaron are also singular at λ=λ(c). This result is representative of all polarons with coupling depending on k and q, and will have important experimental consequences (e.g., in angle-resolved photoemission spectroscopy and conductivity experiments).
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.
authors.forename: D J J
authors.initials: DJ
authors.lastname: Marchand
authors.forename: G
authors.initials: G
authors.lastname: De Filippis
authors.forename: V
authors.initials: V
authors.lastname: Cataudella
authors.forename: M
authors.initials: M
authors.lastname: Berciu
authors.forename: N
authors.initials: N
authors.lastname: Nagaosa
authors.forename: N V
authors.initials: NV
authors.lastname: Prokof'ev
authors.forename: A S
authors.initials: AS
authors.lastname: Mishchenko
authors.forename: P C E
authors.initials: PC
authors.lastname: Stamp