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Nature: SJTU Team Revealed Moiré Lattice Medium Wave’s Evolution Rule

December 19, 2019      Author: School of Physics and Astronomy

Recently, taking the localization of light waves as an example, Ye Fangwei's research team from SJTU's School of Physics and Astronomy, cooperated with Chen Xianfeng's team, took the lead in discovering and revealing a new wave packet localization mechanism: an extremely flat band structure based on moiré lattices. This discovery is of important physical significance and can be applied widely.

Moiré lattices give us a new way to control light. With them, we can find a simpler and easier method for future beam control, image transmission, and information processing. They also provide an easy-to-implement platform for studying nonlinear optics at low power. In addition, the study of photon moiré lattices also provides extremely useful reference for the study of moiré lattices in two-dimensional materials and cold atom systems.

On December 18, the research result was published online in the top internationally renowned journal Nature under the title "Localization and delocalization of light in photonic moiré lattices". The first author is Ph.D. Wang Peng and Assistant Researcher Zheng Yuanlin. The paper's collaborators include Prof. Chen Xianfeng of Shanghai Jiao Tong University, Dr. Huang Changming of Shanxi Changzhi College, Dr. Yaroslav Kartashov (Russia), Prof. Lluis Torner (Spain) and Prof. Vladimir Konotop (Portugal). Prof. Ye Fangwei is the correspondence author, and Shanghai Jiao Tong University is the sole correspondence institution.

Ye Fangwei's team has long studied the new physics of light-matter interaction, and explored the new ways of light control. The team expressed thanks to Prof. Chen Xianfeng's team for their experimental cooperation, National and Shanghai Municipal Natural Science Foundation for the funding, and SJTU Network & Information Center for the cloud computing support to a large number of numerical calculations.



Moiré lattices consist of two superimposed identical periodic structures with a relative rotation angle. Moiré lattices have several applications in everyday life, including artistic design, the textile industry, architecture, image processing, metrology and interferometry. For scientific studies, they have been produced using coupled graphene-hexagonal boron nitride monolayers1,2, graphene-graphene layers3,4 and graphene quasicrystals on a silicon carbide surface5. The recent surge of interest in moiré lattices arises from the possibility of exploring many salient physical phenomena in such systems; examples include commensurable-incommensurable transitions and topological defects2, the emergence of insulating states owing to band flattening3,6, unconventional superconductivity4 controlled by the rotation angle7,8, the quantum Hall effect9, the realization of non-Abelian gauge potentials10 and the appearance of quasicrystals at special rotation angles11. A fundamental question that remains unexplored concerns the evolution of waves in the potentials defined by moiré lattices. Here we experimentally create two-dimensional photonic moiré lattices, which-unlike their material counterparts-have readily controllable parameters and symmetry, allowing us to explore transitions between structures with fundamentally different geometries (periodic, general aperiodic and quasicrystal). We observe localization of light in deterministic linear lattices that is based on flat-band physics6, in contrast to previous schemes based on light diffusion in optical quasicrystals12, where disorder is required13 for the onset of Anderson localization14 (that is, wave localization in random media). Using commensurable and incommensurable moiré patterns, we experimentally demonstrate the two-dimensional localization-delocalization transition of light. Moiré lattices may feature an almost arbitrary geometry that is consistent with the crystallographic symmetry groups of the sublattices, and therefore afford a powerful tool for controlling the properties of light patterns and exploring the physics of periodic-aperiodic phase transitions and two-dimensional wavepacket phenomena relevant to several areas of science, including optics, acoustics, condensed matter and atomic physics.

Paper Link:https://www.nature.com/articles/s41586-019-1851-6


Translated by Chen Qianqian     Reviewed by Wang Bingyu