Tunable nonlinear excitonic optical response in biased bilayer graphene

TL;DR

This paper investigates how the excitonic optical response of biased bilayer graphene can be tuned via gate voltage, affecting both linear and nonlinear responses, including second harmonic generation.

Contribution

It provides a semi-analytical model linking gate voltage to excitonic binding energies and optical responses in bilayer graphene, highlighting tunability of nonlinear effects.

Findings

Optical responses are highly sensitive to gate voltage changes.

Both linear and nonlinear (SHG) responses vary significantly with bias.

The model predicts tunable excitonic effects in bilayer graphene.

Abstract

Biased bilayer graphene (BBG) is an important system for studies of excitonic effects in graphene--based systems, with its easily tunable bandgap. This bandgap is governed by an external gate voltage, allowing one to tune the optical response of the system. In this paper, we study the excitonic linear and nonlinear optical response of Bernal stacked BBG as a function of the gate voltage, both for in--plane (IP) and out--of--plane (OOP) directions. Based on a semi-analytical model of the electronic structure of BBG describing the influence of gate voltage on excitonic binding energies, we focus our discussion on both the IP and OOP excitonic response. Both linear and second harmonic generation (SHG) nonlinear responses are shown to be very sensitive to the gate voltage, as both the interband momentum matrix elements and the bandgap of the system will vary greatly with bias potential.