New method to controlling moiré flatbands changes band balanced out of two photonic lattices.
When two lattices with distinct angles or periodicities come together, they conjure a moiré superlattice– a realm where impressive phenomena like superconductivity and optical solitons spring to life. At the heart of this realm lies the moiré flatband, a key gamer in shaping sophisticated light– matter interactions, such as laser emission and 2nd harmonic generation. In moiré physics and its appropriate applications, wielding control over flatbands is a critical superpower.
Getting and Controlling Moiré Flatbands
Moiré flatbands are generally produced with special structures, typically controlled through a dance of rotation angles (magic angle) and spacings (magic distance) in between the 2 lattice layers. Recently, a collective research team from University of Electronic Science and Technology of China, Anqing Normal University, Guangxi University, and Nankai University proposed a new way to control moiré flatbands, by changing the band offset of 2 photonic lattices in the specification area.
A bilayer moiré superlattice permits band offsets to be adjusted by varying the thickness of one layer. Credit: Peilong Hong
As reported in Advanced Photonics Nexus, the group discovered that, in addition to flatbands that wink in and out of existence as the band balanced out modifications, two robust groups of flatbands can develop within a broad series of band balanced out. Their consistent presence eases stringent control of structural specifications for getting a nontrivial superlattice, opening brand-new chances in moiré photonics. By modifying structural criteria, the resonant frequencies of these robust flatbands can be changed, enabling the creation of unique multiresonant moiré devices.
The Research Methodology
How did they accomplish this advancement? They began with a mismatched silicon-based bilayer moiré superlattice and adjusted the band balanced out by differing the thickness of one layer of the superlattices. By calculating the superlattice band structure at different band offsets, they observed that band balance out successfully controls the moiré flatbands, consisting of appearance and disappearance of some flatbands in the superlattice. Concurrently, they found that particular moiré flatbands remain gradually within a broad series of band offset.
Ramifications of Robust Flatbands
The robustness of these flatbands unveils a secret: crafting remarkable moiré superlattices does not require precise lattice control, yet it grants the power to tune moiré flatband resonance frequencies through band balance out changes. As a testimony to this power, the scientists systematically investigated the localized modes stemming from the two groups of robust flatbands in moiré superlattices with finite size, validating the feasibility of top quality two times as resonant moiré superlattices.
System Behind Flatband Formation
To elucidate the system behind robust flatband development, the authors proposed an easy yet efficient diagrammatic model based on the coupled-mode theory, taking into account the structural characteristics of the moiré superlattices. The model revealed the similarities and distinctions in the development of these flatbands. For additional confirmation, the authors included full-wave calculations into the diagrammatic model, and effectively anticipated the field circulation of these robust flatbands.
Conclusion and Future Prospects
This advance opens new horizons for uncharted paths in moiré physics: controlling moiré flatbands by tuning the band offset in parameter space is an elegantly basic method that holds the crucial to unlocking nontrivial superlattices and deciphering the mysteries of flatband development and disappearance. Theres more– the diagrammatic design isnt just a tool; its a window into the world of flatband development across diverse moiré superlattices.
Reference: “Robust moiré flatbands within a broad band-offset range” by Peilong Hong, Yi Liang, Zhigang Chen, Guoquan Zhang, 28 September 2023, Advanced Photonics Nexus.DOI: 10.1117/ 1. APN.2.6.066001.
By computing the superlattice band structure at different band offsets, they observed that band offset successfully manages the moiré flatbands, including look and disappearance of some flatbands in the superlattice. All at once, they found that particular moiré flatbands stay gradually within a broad range of band offset.
To illuminate the system behind robust flatband formation, the authors proposed a simple yet reliable diagrammatic design based on the coupled-mode theory, taking into account the structural characteristics of the moiré superlattices. This advance opens new horizons for uncharted courses in moiré physics: managing moiré flatbands by tuning the band balanced out in parameter area is an elegantly easy approach that holds the essential to unlocking nontrivial superlattices and deciphering the mysteries of flatband emergence and disappearance. Theres more– the diagrammatic model isnt just a tool; its a window into the world of flatband development throughout diverse moiré superlattices.