Quasienergy spectra of graphene dots in intense ac fields: Field anisotropy and photon-dressed quantum rings

Abstract

A graphene quantum dot under intense ac field and static low magnetic field is investigated. From a tight-binding perspective, applying a Fourier-Floquet transformation and renormalization process, we observe that graphene-intrinsically anisotropic-reveals field polarization signatures in the quasidensity of states. For the ac field polarized along the armchair direction, the dressed electronic structure shows an emergent property: an ac-field-induced quantum ring. This is inferred by the orientation-dependent formation of a miniband of energy states periodically modulated with increasing magnetic field, exactly analogous to the behavior of a quantum-ring spectrum.

Dynamic band collapse in photonic graphene

“…where we have set and where k = k x u x + k y u y is the electron quasi-momentum. Equations (11)- (14) generalize, in the case of an arbitrarily polarized ac field, the quasi-energy band calculation previously reported in [15] for graphene in a linearly-polarized field, and enable us to predict the occurrence of partial or complete collapse of valence ( − ) and conduction ( + ) quasi-energy bands depending on the polarization state of the driving field. A partial band collapse is obtained whenever two of the three parameters 1 , 2 and 3 are the roots of the J 0 Bessel function, whereas complete band collapse requires that all of them are roots of J 0 .…”

“…At a Dirac point, electrons behave effectively as relativistic massless Dirac fermions, a circumstance that has led to the observation of condensed-matter analogues of the physics of relativistic electrons, such as Klein tunnelling and Zitterbewegung (see, for instance, [2][3][4]). Several recent works have suggested the possibility of engineering the band structure and the electronic transport properties in graphene by application of electric and/or magnetic fields [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], for example to open dynamic band gaps. This has lead to the prediction of a variety of phenomena, such as the photovoltaic Hall effect [7], metal-insulator transition [8], valley-polarized currents in both monolayer and bilayer graphene [9,10], and the photoinduced quantum Hall effect in the absence of magnetic fields [11].…”

Unpaired Floquet Majorana fermions without magnetic fields

“…with the energies given in Eq. (22). These states are, indeed, eigenstates of each blockĤ (0) +m Ω of the Floquet operator given in Eq.(A4).…”

Spin and electronic correlations in gated graphene quantum rings

“…32,33 The electronic properties of a single Dirac Fermion in graphene quantum rings were studied using effective mass 34,35 and tight-binding ͑TB͒ methods. 34,36,37 Valley degeneracy in graphene was shown to be lifted by the magnetic field 34,36 since the magnetic field has the opposite sign in the two valleys. The AB effect was also studied in Refs.…”