Orbital-dependent Electron-Hole Interaction in Graphene and Associated Multi-Layer Structures.

ABSTRACT: We develop an orbital-dependent potential to describe electron-hole interaction in materials with structural 2D character, i.e. quasi-2D materials. The modulated orbital-dependent potentials are also constructed with non-local screening, multi-layer screening, and finite gap due to the coupling with substrates. We apply the excitonic Hamiltonian in coordinate-space with developed effective electron-hole interacting potentials to compute excitons' binding strength at M (? band) and ? (? band) points in graphene and its associated multi-layer forms. The orbital-dependent potential provides a range-separated property for regulating both long- and short-range interactions. This accounts for the existence of the resonant ? exciton in single- and bi-layer graphenes. The remarkable strong electron-hole interaction in ? orbitals plays a decisive role in the existence of ? exciton in graphene stack at room temperature. The interplay between gap-opening and screening from substrates shed a light on the weak dependence of ? exciton binding energy on the thickness of graphene stacks. Moreover, the analysis of non-hydrogenic exciton spectrum in quasi-2D systems clearly demonstrates the remarkable comparable contribution of orbital dependent potential with respect to non-local screening process. The understanding of orbital-dependent potential developed in this work is potentially applicable for a wide range of materials with low dimension.

SUBMITTER: Deng T 

PROVIDER: S-EPMC4661528 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature