Dynamical polarizability of graphene irradiated by circularly polarized ac electric fields

Abstract

We examine the low-energy physics of graphene in the presence of a circularly polarized electric field in the terahertz regime. Specifically, we derive a general expression for the dynamical polarizability of graphene irradiated by an ac electric field. Several approximations are developed that allow one to develop a semianalytical theory for the weak field regime. The ac field changes qualitatively the single and many electron excitations of graphene: undoped samples may exhibit collective excitations (in contrast to the equilibrium situation), and the properties of the excitations in doped graphene are strongly influenced by the ac field. We also show that the intensity of the external field is the critical control parameter for the stability of these excitations.

Non-perturbative effects of laser illumination on the electrical properties of graphene nanoribbons

“…Further studies focused on the optical response [17,19] as well as other interesting issues [20,21,22,23]. Recently, the possibility of inducing topologically protected states by laser illumination in semiconductors [24] and both in monolayer [25,26] and bilayer [27] graphene has become a hot field [28,29] with an impact on other areas such as condensates [30] and photonic crystals, where experiments are already available [31].…”

Merging of Dirac points and Floquet topological transitions in ac-driven graphene

“…Importantly, at lower frequencies, we find that the coupling between the Floquet bands, that characterize the properties of the driven system, gives rise to out-of-equilibrium phases with no analogue in the static system in which multiple PDPs emerge. Our approach does not rely either on low-energy models or on approximations valid just close to resonance (as the rotating wave approximation), 8,9,26 but takes into account the full lattice model together with arbitrary field amplitudes and phase polarizations. This allows us to keep track of the relative position between the Dirac points and thus properly describe their annihilation or creation.…”

Dielectric function, screening, and plasmons of graphene in the presence of spin-orbit interactions

“…These extensions range from numerical 11,12 and analytical 13 tight-binding studies and the inclusion of a finite band gap [14][15][16] to double-and multilayer graphene samples, [17][18][19][20][21][22] graphene antidot lattices, 23 and graphene under a circularly polarized ac electric field. 24 In this work we study the dielectric properties of graphene including both the Rashba and the intrinsic spin-orbit coupling. While the case of purely intrinsic interactions is well understood, [14][15][16] the dielectric function for the general case, where both types of SOIs are present, is unknown.…”