Phase transition of polarons in bilayer graphene nanoribbons

Abstract

Abstract Stacking graphene nanoribbons (GNRs) is the natural path to obtain semiconductors with exotic quantum phenomena by manipulating the interlayer coupling. Recently, a report demonstrated that, during charge transport, interlayer coupling significantly affects the phonon breathing modes. Therefore, a reliable physical description of charged carriers must explicitly address the coupling nature of the electronic and lattice phenomena. In this work, we gauge the influence of interlayer coupling (t ⊥) on the formation of charged carriers in a bilayer of an armchair graphene nanoribbon using a model Hamiltonian with electron-phonon coupling. We find different quasiparticle solutions depending on the t ⊥ magnitude. As it increases, the carrier’s charge progressively delocalizes along the layers, resulting in two interlayer polaron morphologies: the non-symmetric (0 meV <t ⊥ ≤ 45 meV) and the symmetric (t ⊥> 45 meV). These solutions also manifest in the band structure through first-order electronic phase transitions in the intragap states with a significant energy shift of about 0.3 eV. Consequently, the carrier’s mobility and effective mass are expected to be highly sensitive to t ⊥, suggesting that mechanical stress can regulate the mechanism. The findings extend to other GNR bilayers, potentially inspiring the development of novel nanoelectronics based on highly confined stacked systems.