Inclined junction in monolayer graphene: A gateway toward tailoring valley polarization of Dirac fermions

TL;DR

This paper demonstrates how a tilted PN junction in monolayer graphene can induce valley-resolved chiral transport, enabling valley polarization control while maintaining high mobility, with potential applications in valleytronics.

Contribution

Introducing a tilted PN junction in graphene to achieve valley contrast through anisotropic chiral transport, a novel method for valley polarization control in isotropic Dirac systems.

Findings

Tilted junction shifts angular spectrum to larger angles.

Valley-resolved chiral transport is achieved.

System remains resilient to edge disorder.

Abstract

Generating discernible valley contrasts and segregating valley-indexed fermions in real space within graphene poses considerable challenges due to the isotropic transport within the continuum energy range for degenerate valleys. This study unveils an interesting finding: introducing valley contrast through anisotropic chiral transport in isotropic Dirac systems like graphene, achieved by implementing a tilted PN junction. The tilted junction shifts the angular spectrum to larger angles in accordance with the tilt angle. This modifies the pseudospin-conserved modes across the junction, resulting in valley-resolved chiral transport. This approach not only induces valley splitting within the real space but also preserves the remarkable mobility of fermions, offering distinct advantages over alternative strategies. The comprehensive analysis includes optimizing the experimental setup, scrutinizing factors such as the sequence of the doped region, and examining critical parameters like the tilt angle delta and transition width d across the junction. Surprisingly, an increased transition width enhances transmission, attributed to specular edge scattering. Importantly, the system remains resilient to Anderson short-range edge disorder. The broader implication lies in the transformative potential of inducing analogous anisotropic chiral transport behaviors in isotropic Dirac systems, resembling the characteristics of tilted Dirac-Weyl semimetals, by incorporating a tilted PNJ.