When two layers of graphene are placed one by one on top of the other and twisted between them at a small angle, a "moiré pattern" is formed, and the physical properties of the system have been proven to happen huge change. In particular, when the "magic" angle is close to 1 degree, the electrons decelerate significantly, which is conducive to the interaction between the electrons. This interaction creates a new type of superconducting and insulating phase in the twisted double-layer graphene. Together with many other fascinating properties discovered in the past three years, this material has been shown to exhibit extremely rich physical phenomena, but most importantly, it has proven to be an easy-to-control quantum material. Now, even if this kind of material made of carbon exhibits such an amazingly diverse state, the interaction between the twisted double-layer graphene and light has shown fascinating results on a theoretical level, but so far there has not been any Experiments can clearly show how this interaction works.
In a recent work published in Nature Physics, the Institute of Photonic Sciences (ICFO) researchers Niels Hesp, Iacopo Torre, David Barcons-Ruiz, and Hanan Herzig Sheinfux were led by ICREA Professor of ICFO Frank Koppens, and the professors The research team of Pablo Jarillo-Herrero (Massachusetts Institute of Technology), Professor Marco Polini (University of Pisa), Professor Efthimios Kaxiras (Harvard), Professor Dmitri Efetov (ICFO) and NIMS (Japan) found that twisted double-layer graphene can be used Guide and control nano-level light. This is possible due to the interaction between light and the collective movement of electrons in the material.
By using the properties of plasmons, in which electrons and light move together as a coherent wave, scientists can observe that plasmons propagate in the material while being strongly confined in the material down to the nanometer level. In addition, by observing the unusual collective optical phenomena that occur in the material, they can understand the special nature of electrons. This observation of propagating light is limited to the nanometer level and can be used as a platform for optical sensing of gases and biomolecules.
To obtain the results of this discovery, the team used a near-field microscope, which can probe optical properties with a spatial resolution of 20 nanometers, which exceeds the diffraction limit. In short, the scientists took two layers of graphene, placed them one by one on top of the other, and at the same time twisted them to a position close to the magic angle, and then irradiated the nano-sized graphene with infrared light at room temperature. Point on the material. They found that the behavior of plasmons is very different from the usual plasmons. For example, in metals or graphene, this deviation is related to the special movement of electrons in the double-layer graphene moiré superlattice.
This work laid the first stone for the nano-optical study of the bizarre phase of twisted double-layer graphene at low temperatures. In particular, it proves that twisted double-layer graphene is an extraordinary nanophotonic material, especially because it serves as an intrinsic (no external voltage required) host for collective excitation.
-This press release was originally published on the ICFO-Institute of Photonic Sciences website
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