Quantum Wires and Waveguides Formed in Graphene by Strain

TL;DR

This paper demonstrates that mechanical strain in graphene can create quantum wires and dots, enabling electron confinement and ballistic transport, which could lead to novel strain-based electronic devices.

Contribution

It introduces a method to form quantum wires in graphene via strain-induced folds, showing their potential for straintronic applications and electron confinement.

Findings

Observation of Coulomb blockade in strained graphene regions

Ballistic transport observed up to ~1 micron along folds

Theoretical predictions of valley-polarized currents in strained regions

Abstract

Confinement of electrons in graphene to make devices has proven to be a challenging task. Electrostatic methods fail because of Klein tunneling, while etching into nanoribbons requires extreme control of edge terminations, and bottom-up approaches are limited in size to a few nanometers. Fortunately, its mechanical flexibility raises the possibility of using strain to alter graphene's properties and create novel straintronic devices. Here, we report transport studies of nanowires created by linearly-shaped strained regions resulting from individual folds formed by layer transfer onto hexagonal boron nitride. Conductance measurements across the folds reveal Coulomb blockade signatures, indicating confined charges within these structures, which act as quantum dots. Along folds, we observe sharp features in traverse resistivity measurements, attributed to an amplification of the dot conductance modulations by a resistance bridge incorporating the device. Our data indicates ballistic transport up to ~1 um along the folds. Calculations using the Dirac model including strain are consistent with measured bound state energies and predict the existence of valley-polarized currents. Our results show that graphene folds can act as straintronic quantum wires.