Band-Selective Filter in a Zigzag Graphene Nanoribbon

TL;DR

This paper investigates electron transport in zigzag graphene nanoribbons, revealing a band index selection rule that enables band-selective filtering and explains the valley-valve effect, with potential experimental observation through conductance measurements.

Contribution

It introduces a band index selection rule in zigzag graphene nanoribbons and demonstrates how barrier potentials can be used as band-selective filters, advancing understanding of electron transport.

Findings

Selection rule preserves wavefunction parity in even-chain ribbons.

Barrier potential tuning enables band-selective electron transmission.

Proposed conductance experiments to observe the selection rule.

Abstract

Electric transport of a zigzag graphene nanoribbon through a step-like potential or a barrier potential is investigated by using the recursive Green's function method. In the case of the step-like potential, we demonstrate numerically that scattering processes obey a selection rule for the band indices when the number of zigzag chains is even; the electrons belonging to the ``even'' (``odd'') bands are scattered only into the even (odd) bands so that the parity of wavefunctions is preserved. The so-called valley-valve effect can be explained by this selection rule. In the case of the barrier potential, by tuning the barrier height to be an appropriate value, we show that it can work as the ``band-selective filter'', which transmits electrons selectively with respect to the indices of the bands to which the incident electrons belong. Finally, we suggest that this selection rule can be observed in the conductance by applying two barrier potentials.