In-plane photoelectric effect in phosphorene nanoribbons

Abstract

Recently, a new photoelectric phenomenon dubbed in-plane photoelectric (IPPE) effect has been demonstrated experimentally. In this work, we investigate the IPPE effect in a zigzag-edged or armchair-edged phosphorene nanoribbons (ZPNRs or APNRs) that is modulated by a step barrier. Based on the Floquet theory, we calculate the directed photocurrent Ī|| (Ī⊥) generated by a non-resonant linearly-polarized light with polarization vector in parallel with (perpendicular to) the nanoribbon direction. We find that such a photocurrent depends on the edge type of the nanoribbon and the polarization direction of light. At high Fermi energies, the IPPE current Ī|| in APNRs is significantly stronger than that in ZPNRs under the same conditions. In APNRs, both Ī|| and Ī⊥ always have the same direction and |Ī||:Ī⊥|>10. In contrast, in ZPNRs Ī⊥ can reverse its direction (becoming negative) and is comparable to Ī|| in amplitude. The negative photocurrent arises from both the photon-emission and photon-absorption process related to the quasi-flat-band in ZPNRs. This indicates that the mid-gap states can be detected by the IPPE effect. The energy scope and amplitude of negative photocurrent can be tuned by adjusting the height of the step barrier, the light frequency, and the light intensity.