Intense Laser Pulse Interaction With Graphene and Graphene Ribbons

Area of Science:

• Quantum mechanics
• Condensed matter physics
• Materials science

Background:

• Graphene's unique electronic properties make it a candidate for advanced optical and electronic devices.
• Understanding light-matter interactions in graphene is crucial for harnessing its potential.

Purpose of the Study:

• To investigate quantum mechanically the interaction of intense ultrashort laser pulses with graphene monolayers and armchair graphene ribbons.
• To analyze the resulting electronic dynamics, including population excitation, interband and intraband correlations, and induced currents.
• To compare the behavior of 2D graphene monolayers with 1D graphene ribbons under laser irradiation.

Main Methods:

• Utilized a tight-binding (TB) Hamiltonian for monolayer graphene.
• Developed rules to derive dispersion relations for armchair graphene ribbons of any width from monolayer TB eigenvalues.
• Numerically solved coupled equations for band amplitudes to determine time-dependent wavefunctions and expectation values.
• Simulated population excitation, interband/intraband correlations, and currents in monolayer and ribbon structures.
• Investigated the dependence of ribbon currents on the carrier-envelope-phase (CEP) of the laser pulse.

Main Results:

• A transition in current dominance was observed from intraband (steady total current) in monolayers to interband (oscillatory current) in ribbons.
• This transition is attributed to dimensional confinement and the finite band gap in ribbons.
• Radiation spectra showed similar structures for both monolayer and ribbon, suggesting dominance of virtual continuum-continuum transitions.
• Charge currents in ribbons were found to be reversible by altering the laser pulse's CEP.
• The pulse shape of charge carriers in ribbons can be engineered by tailoring the laser's vector potential.

Conclusions:

• Graphene ribbons exhibit distinct current dynamics compared to monolayers when interacting with ultrashort laser pulses.
• The dimensional confinement and band structure of ribbons significantly influence charge carrier behavior.
• Carrier-envelope-phase manipulation offers a pathway to control and design charge carrier dynamics in graphene ribbons.
• Further investigation is needed to fully elucidate the observed transition in current dominance.