Mach--Zehnder-like interferometry with graphene nanoribbon networks

TL;DR

This paper theoretically investigates electron interference in a graphene nanoribbon network configured as a Mach--Zehnder interferometer, demonstrating tunable interference effects and potential applications in sensing and quantum entanglement.

Contribution

It introduces a model for graphene nanoribbon-based interferometers with tunable junctions, providing a simplified scattering matrix approach validated against Green's function calculations.

Findings

Interference patterns are sensitive to magnetic flux and geometric variations.

The scattering matrix approach accurately predicts transport properties.

Potential applications include magnetic sensors and quantum entanglement studies.

Abstract

We study theoretically electron interference in a Mach--Zehnder-like geometry formed by four zigzag graphene nanoribbons (ZGNRs) arranged in parallel pairs, one on top of the other, such that they form intersection angles of 60$^\circ$. Depending on the interribbon separation, each intersection can be tuned to act either as an electron beam splitter or as a mirror, enabling tuneable circuitry with interfering pathways. Based on the mean-field Hubbard model and Green's function techniques, we evaluate the electron transport properties of such 8-terminal devices and identify pairs of terminals that are subject to self-interference. We further show that the scattering matrix formalism in the approximation of independent scattering at the four individual junctions provides accurate results as compared with the Green's function description, allowing for a simple interpretation of the interference process between two dominant pathways. This enables us to characterize the device sensitivity to phase shifts from an external magnetic flux according to the Aharonov--Bohm effect as well as from small geometric variations in the two path lengths. The proposed devices could find applications as magnetic field sensors and as detectors of phase shifts induced by local scatterers on the different segments, such as adsorbates, impurities or defects. The setup could also be used to create and study quantum entanglement.