Abstract
Motivated by the recent experimental realization of twisted double bilayer graphene (TDBG) samples, we study, both analytically and numerically, the effects of circularly polarized light propagating in free space and confined in a waveguide on the band structure and topological properties of these systems. These two complementary Floquet protocols allow us to selectively tune different parameters of the system by varying the intensity and light frequency. For the drive protocol in free space, in the high-frequency regime, we find that in TDBG with AB/BA stacking, we can selectively close the zone-center quasienergy gaps around one valley while increasing the gaps near the opposite valley by tuning the parameters of the drive. In TDBG with AB/AB stacking, a similar effect can be obtained upon the application of a perpendicular static electric field. Furthermore, we study the topological properties of the driven system in different settings, provide accurate effective Floquet Hamiltonians, and show that relatively strong drives can generate flat bands. On the other hand, longitudinal light confined in a waveguide couples to the components of the interlayer hopping that are perpendicular to the TDBG sheet, allowing for selective engineering of the bandwidth of Floquet zone-center quasienergy bands without breaking the symmetries of the static system.5 MoreReceived 15 June 2020Accepted 1 September 2020DOI:https://doi.org/10.1103/PhysRevResearch.2.033494Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectronic structureTwist deformationValleytronicsPhysical SystemsFloquet systemsGrapheneTopological insulatorsTechniquesBand structure methodsCondensed Matter, Materials & Applied Physics
Highlights
Moiré superlattices have emerged as platforms to attain strongly correlated phases of matter by controlling the stacking configuration between the layers [1,2,3]
On the other hand, using light confined to a waveguide allows us to dynamically tune the component of the tunneling perpendicular to the plane without breaking the symmetries of the static system
We have studied twisted double bilayer graphene driven by circularly polarized light in free space and confined to a waveguide
Summary
Moiré superlattices have emerged as platforms to attain strongly correlated phases of matter by controlling the stacking configuration between the layers [1,2,3]. In the presence of a transverse electric field, driven AB/AB TDBG allows the quasienergy gaps at the K and K valleys to be selectively tuned by varying the direction of the static electric field and by modulating the amplitude and frequency of the driving laser. The flexibility of the quasienergy band structure near the Floquet zone center can be used to generate valley polarized currents in TDBG, independent of the stacking configuration. III we consider TDBG driven by circularly polarized light in free space We consider both high- and intermediate-frequency regimes and describe the effects on the band structure and the topological aspects in each regime.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
