Scattering of two-dimensional Dirac fermions on gate-defined oscillating quantum dots

TL;DR

This paper investigates how massless Dirac fermions in graphene scatter off oscillating quantum dots, revealing inelastic effects, resonance modifications, and potential for controlling electron propagation through time-dependent barriers.

Contribution

It introduces a theoretical model for scattering of Dirac fermions on oscillating quantum dots, highlighting the impact of time-dependent potentials on scattering resonances and inelastic processes.

Findings

Oscillating quantum dots cause inelastic scattering and energy shifts.

Resonances in static dots are modified or dissolved by oscillation.

Finite scattering efficiency persists at low energies despite oscillations.

Abstract

Within an effective Dirac-Weyl theory we solve the scattering problem for massless chiral fermions impinging on a cylindrical time-dependent potential barrier. The set-up we consider can be used to model the electron propagation in a monolayer of graphene with harmonically driven quantum dots. For static small-sized quantum dots scattering resonances enable particle confinement and interference effects may switch forward scattering on and off. An oscillating dot may cause inelastic scattering by excitation of states with energies shifted by integer multiples of the oscillation frequency, which significantly modifies the scattering characteristics of static dots. Exemplarily the scattering efficiency of a potential barrier with zero bias remains finite in the limit of low particle energies and small potential amplitudes. For an oscillating quantum dot with finite bias, the partial wave resonances at higher energies are smeared out for small frequencies or large oscillation amplitudes, thereby dissolving the quasi-bound states at the quantum dot.