Spatial Confinement, Magnetic Localization and Their Interactions on Massless Dirac Fermions

TL;DR

This study visualizes and analyzes how spatial confinement and magnetic fields influence massless Dirac fermions in graphene, revealing effects like Landau level formation and Berry phase jumps, crucial for graphene-based electronic devices.

Contribution

It experimentally demonstrates the interplay of spatial confinement and magnetic localization on Dirac fermions in an angled graphene wedge, highlighting the impact on Landau levels and Berry phase behavior.

Findings

Visualization of quasibound states in graphene wedge

Magnetic fields induce Landau levels in confined Dirac fermions

Observation of Berry phase jump related to Klein tunneling

Abstract

It is of keen interest to researchers understanding different approaches to confine massless Dirac fermions in graphene, which is also a central problem in making electronic devices based on graphene. Here, we studied spatial confinement, magnetic localization and their interactions on massless Dirac fermions in an angled graphene wedge formed by two linear graphene p-n boundaries with an angle 34. Using scanning tunneling microscopy, we visualized quasibound states temporarily confined in the studied graphene wedge. Large perpendicular magnetic fields condensed the massless Dirac fermions in the graphene wedge into Landau levels (LLs). The spatial confinement of the wedge affects the Landau quantization, which enables us to experimentally measure the spatial extent of the wave functions of the LLs. The magnetic fields induce a sudden and large increase in energy of the quasibound states because of a pi Berry phase jump of the massless Dirac fermions in graphene. Such a behavior is the hallmark of the Klein tunneling in graphene. Our experiment demonstrated that the angled wedge is a unique system with the critical magnetic fields for the pi Berry phase jump depending on distance from summit of the wedge.