Interplay of relativistic and nonrelativistic transport in atomically precise segmented graphene nanoribbons

TL;DR

This paper investigates electrical transport in atomically-precise segmented graphene nanoribbons, combining NEGF calculations and a Dirac continuum model to understand relativistic and nonrelativistic carrier behaviors and interference effects.

Contribution

It introduces a unified Dirac continuum model that accurately reproduces NEGF results, elucidating relativistic and nonrelativistic transport phenomena in segmented graphene nanoribbons.

Findings

Optical Dirac Fabry-Perot oscillations in metallic armchair SGNRs

Unequal Fabry-Perot patterns in mixed armchair-zigzag SGNRs

Continuum model effectively reproduces NEGF conductance results

Abstract

Graphene's isolation launched explorations of fundamental relativistic physics originating from the planar honeycomb lattice arrangement of the carbon atoms, and of potential technological applications in nanoscale electronics. Bottom-up fabricated atomically-precise segmented graphene nanoribbons, SGNRs, open avenues for studies of electrical transport, coherence, and interference effects in metallic, semiconducting, and mixed GNRs, with different edge terminations. Conceptual and practical understanding of electric transport through SGNRs is gained through nonequilibrium Green's function (NEGF) conductance calculations and a Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. The continuum model reproduces the NEGF results, including optical Dirac Fabry-Perot (FP) equidistant oscillations for massless relativistic carriers in metallic armchair SGNRs, and an unequally-spaced FP pattern for mixed armchair-zigzag SGNRs where carriers transit from a relativistic (armchair) to a nonrelativistic (zigzag) regime. This provides a unifying framework for analysis of coherent transport phenomena and interpretation of forthcoming experiments in SGNRs.