Imaging backscattering in graphene quantum point contacts

Abstract

We study graphene quantum point contacts (QPC) and imaging of the backscattering of the Fermi level wave function by potential introduced by a scanning probe. We consider both etched single-layer QPCs as well as the ones formed by bilayer patches deposited at the sides of the monolayer conducting channel using an atomistic tight binding approach. A computational method is developed to effectively simulate an infinite graphene plane outside the QPC using a computational box of a finite size. We demonstrate that in spite of the Klein phenomenon interference due to the backscattering at a circular n-p junction induced by the probe potential is visible in spatial maps of conductance as functions of the probe position.Comment: 8 pages, 14 figure

Optimizing Dirac fermions quasi-confinement by potential smoothness engineering

“…Scanning gate microscopy (SGM) consists in scanning an electrically polarized metallic tip, acting as a local gate above a device's surface, and mapping out tip-induced device's conductance changes [33]. Initially developed to investigate transport in III-V semiconductor heterostructures [34][35][36][37], SGM brought spatially-resolved insights into transport phenomena occurring in graphene devices, through experiments, simulations and their combination [38][39][40][41][42][43][44][45][46][47][48]. Recently, we demonstrated the viability of SGM to study ballistic transport in clean encapsulated graphene devices, and reported optical-like behavior of Dirac fermions using the tip-induced potential as a Veselago lens [49].…”

Imaging Dirac fermions flow through a circular Veselago lens

“…However, very few SGM experiments have been conducted yet on clean encapsulated graphene devices. Hence, it has proven difficult to observe electronoptics behavior in graphene using SGM, despite several theoretical predictions [34][35][36].…”

Imaging signatures of the local density of states in an electronic cavity

“…There are two common approaches to evaluating the transport properties of non-interacting mesoscopic devices, which have been used extensively to understand SGM measurements: semi-classical expansions [22,[36][37][38], and tight-binding calculations [15,[39][40][41]. The former is formulated in terms of the classical trajectories of electrons exiting the QPC.…”