Floquet engineering of twisted double bilayer graphene
Floquet engineering of twisted double bilayer graphene
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DOI：
10.1103/physrevresearch.2.033494
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发表时间：
2020-06
影响因子：
4.2
通讯作者：
M. Rodriguez-Vega;M. Vogl;G. Fiete
中科院分区：
文献类型：
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作者：
M. Rodriguez-Vega;M. Vogl;G. Fiete
受最近实验实现的扭曲双层石墨烯（TDBG）样品的启发，我们研究，分析和数值计算，圆偏振光在自由空间中传播，并限制到波导上的能带结构和拓扑性质的这些系统的影响。这两个互补的Floquet协议允许我们通过改变光的强度和频率来选择性地调整系统的不同参数。对于自由空间中的驱动协议，在高频区域，我们发现在具有AB/BA堆叠的TDBG中，我们可以通过调整驱动参数来选择性地关闭一个谷附近的区中心准能隙，同时增加相对谷附近的能隙。在具有AB/AB堆叠的TDBG中，在施加垂直静电场时可以获得类似的效果。此外，我们还研究了驱动系统在不同情况下的拓扑性质，提供了精确的有效Floquet哈密顿量，并表明相对较强的驱动器可以产生平坦带。另一方面，限制在波导中的纵向光耦合到垂直于TDBG片的层间跳跃的组件，从而允许选择性地设计Floquet区中心准能带的带宽，而不破坏静态系统的对称性。
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 into 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 the frequency of the light. 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 into 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.