A tunable electronic beam splitter realized with crossed graphene nanoribbons

TL;DR

This paper demonstrates a tunable electronic beam splitter using crossed graphene nanoribbons, showing potential for quantum circuits and electron optics with controllable electron wave division.

Contribution

It introduces a novel 4-terminal device with crossed GNRs that acts as a mechanically tunable electron beam splitter, supported by first-principles transport simulations.

Findings

Electron injection can be split into two with ~50% ratio at 60° intersection.

The device can operate as a controllable beam splitter with minimal back-reflection.

Realistic conditions for practical implementation are identified.

Abstract

Graphene nanoribbons (GNRs) are promising components in future nanoelectronics due to the large mobility of graphene electrons and their tunable electronic band gap in combination with recent experimental developments of on-surface chemistry strategies for their growth. Here we explore a prototype 4-terminal semiconducting device formed by two crossed armchair GNRs (AGNRs) using state-of-the-art first-principles transport methods. We analyze in detail the roles of intersection angle, stacking order, inter-GNR separation, and finite voltages on the transport characteristics. Interestingly, when the AGNRs intersect at $\theta= 60^\circ$, electrons injected from one terminal can be split into two outgoing waves with a tunable ratio around 50% and with almost negligible back-reflection. The splitted electron wave is found to propagate partly straight across the intersection region in one ribbon and partly in one direction of the other ribbon, i.e., in analogy of an optical beam splitter. Our simulations further identify realistic conditions for which this semiconducting device can act as a mechanically controllable electronic beam splitter with possible applications in carbon-based quantum electronic circuits and electron optics. We rationalize our findings with a simple model that suggests that electronic beam splitters can generally be realized with crossed GNRs.