Optical characterization of Peierls instability of zigzag-edge phosphorene nanoribbons

It has been demonstrated that the bare zigzag-edge phosphorene nanoribbons (zPNRs) were regularly believed as metals. However, some first-principle work [EPL108, 47005 (2014); PRB94, 075422 (2016)1 suggested that zPNRs could be Peierls-gapped semiconductor due to the edge-reconstructions. In this work, we study the optical characterization of edge-Peierls-instability (EPI) in zPNRs based on the tight-binding calculations. Responding to EPI, an additional infrared absorption can be observed in the polarized-optical-conductivity-spectrum which is resonant to the Peierls gap. This new peak could be either singlet or doublet, which is determined by the ribbons embracing even- or odd-number zigzag chains. Moreover, it is unraveled that the opening of the Peierls gap is intimately related to the formation of the isolated edge-state subbands near the Fermi level.