Abstract
Chirally stacked N-layer graphene is a semimetal with ±pN band-touching at two nonequivalent corners in its Brillioun zone. We predict that an off-resonant circularly polarized light (CPL) drives chirally stacked N-layer graphene into a Floquet Chern insulators (FCIs), aka quantum anomalous Hall insulators, with tunable high Chern number CF = ±N and large gaps. A topological phase transition between such a FCI and a valley Hall (VH) insulator with high valley Chern number Cv = ±N induced by a voltage gate can be engineered by the parameters of the CPL and voltage gate. We propose a topological domain wall between the FCI and VH phases, along which perfectly valley-polarized N-channel edge states propagate unidirectionally without backscattering.
Highlights
The rise of graphene has triggered tremendous efforts to investigate the novel physical properties of its multilayer versions both experimentally and theoretically [1,2,3,4,5,6,7,8]
We demonstrate that periodically driven chirally stacked finite N -layer graphene systems by a left/right circularly polarized light (CPL) can become Floquet Chern insualors (FCIs) with tunable high Chern number ±N just by number of the layers, and a large gap
Based on the above analysis, we know that Floquet mass favors Floquet Chern Insulators (FCIs) phases but staggered potential favor valley Hall (VH) phases, the competition between them will result in topological phase transitions, as shown Fig. 2(a)
Summary
The rise of graphene has triggered tremendous efforts to investigate the novel physical properties of its multilayer versions both experimentally and theoretically [1,2,3,4,5,6,7,8]. The low energy conduction and valence bands in chirally (ABC) stacked N -layer graphene have ±pN dispersion (here p is momentum measured from the two valleys K and K ) and a Berry phase of N π, N times the value of Dirac fermions These unique properties could result in remarkable features such as unusual Landau quantization. The Floquet-Bloch states have been experimentally observed on the surface of photo-excited Bi2Se3 by using time- and angle-resolved photoemission spectroscopy [58, 59] Such topologically nontrivial states with high topological number in controllable manners and a large gap are quite scarce in nature due to their extremely stringent requirements on special band structures and sample quality. Our finds will motivate further investigations on the fascinating properties of periodically driven chirally stacked N -layer graphene systems from both basic and applied research fields
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