Localization of large polarons in the disordered Holstein model

Journal article

We solve the disordered Holstein model via the density-matrix renormalization group method to investigate the combined roles of electron-phonon coupling and disorder on the localization of a single charge or exciton. The parameter regimes chosen, namely the adiabatic regime, ω/4t0=ω′<1, and the large polaron regime, λ<1, are applicable to most conjugated polymers. We show that as a consequence of the polaron effective mass diverging in the adiabatic limit (defined as ω′→0 subject to fixed λ) self-localized, symmetry-breaking solutions are predicted by the quantum Holstein model for infinitesimal disorder, in complete agreement with the predictions of the Born-Oppenheimer Holstein model. For other parts of the (ω′, λ) parameter space, however, self-localized Born-Oppenheimer solutions are not expected. If ω′ is not small enough and λ is not large enough, then the polaron is predominately localized by Anderson disorder, albeit more than for a free particle, because of the enhanced effective mass. Alternatively, for very small electron-phonon coupling (λ1) the disorder-induced localization length is always smaller than the classical polaron size, 2/λ, so that disorder always dominates. We comment on the implication of our results on the electronic properties of conjugated polymers. © 2014 American Physical Society.

Authors: Tozer, O; Barford, W

• Publication status: Published
• Publisher: American Physical Society
• Journal: Physical Review B
• Volume: 89
• Issue: 15
• Publication date: 2014-04-28
• DOI: 10.1103/PhysRevB.89.155434
• EISSN: 1550-235X
• ISSN: 1098-0121
• Language: English