Science & Technology

Researchers observe sound and light pulses in 2D materials for the first time

Research Team, LR: Yuval Adiv, Yaniv Kurman, Professor Ido Kaminer, Raphael Dahan, Dr. Kangpeng Wang.Credit: Technion-Israel Institute of Technology

Space-time symphony of light

Using an ultrafast transmission electron microscope, Technion-Israel Institute of Technology researchers for the first time recorded the propagation of a combination of sound and light in an atomically thin material.

The experiment was conducted at the Robert and Ruth Magid Electrobeam Quantum Mechanics Laboratory, led by Andrew and Erna Bitervi, Faculty of Electrical and Computer Engineering and Professor Id Kaminer of the Solid State Institute.

Single-layer materials, also called 2D materials, are new materials in their own right and are solids consisting of a single layer of atoms. Graphene, the first 2D material discovered, was first isolated in 2004 and won the 2010 Nobel Prize. Now, for the first time, Technion scientists show how light pulses move in these materials. Their discovery, “Spatio-temporal Imaging of 2D Polariton Wave Packet Dynamics Using Free Electrons,” Science Following great interest by many scientists.

Sound waves of 2D material-light waves

Diagram of measurement using sound waves of 2D material and its free electrons.Credit: Technion-Israel Institute of Technology

Light travels in space at 300,000 km / s. Moving in water or in glass will slow down slightly. However, moving a certain number of layers of solids slows the light almost 1000 times. This is because light vibrates the atoms of these special materials to produce sound waves (also called phonons), and when these atomic waves vibrate, they produce light. Therefore, the pulse is actually a tightly coupled combination of sound and light called a “phonon polariton”. When lit up, the material is “singing”.

Scientists radiated light pulses along the edges of the 2D material to generate hybrid sound waves and waves of light within the material. Not only were they able to record these waves, they also found that the pulse could spontaneously accelerate and decelerate. Surprisingly, the wave is split into two separate pulses and travels at different velocities.

The experiment was performed using an ultrafast transmission electron microscope (UTEM). Unlike light microscopy and scanning electron microscopy, particles here pass through the sample and are received by the detector. This process allowed researchers to track sound waves at unprecedented resolutions, both in space and time. Time resolution is 50 femtoseconds – 50X10-15 seconds – the number of frames per second is the same as the number of seconds in a million years.

“Hybrid waves move through the material and cannot be observed with a regular light microscope,” Kerman explains. “Most measurements of light in 2D materials are based on microscopic techniques that use needle-like objects that scan the surface point by point, but all such needle contact is what we try to image. In contrast, our new technology can image the movement of light without disturbing it. Our results could not be achieved by existing methods. Therefore, in addition to our scientific discoveries, we present unprecedented measurement methods related to more scientific discoveries. “

This study was born in the midst of the COVID-19 epidemic. During the months when the university was closed, Yaniv Kurman, a graduate student in Professor Kaminer’s lab, sat at home to see how light pulses should behave in 2D materials and how they can be measured. I made a mathematical calculation to predict. Meanwhile, another student in the same lab, Raphael Dahan, understood how to focus infrared pulses on the group’s electron microscopes and made the necessary upgrades to achieve that. After the blockade, the group was able to prove Kerman’s theory and even reveal additional phenomena they did not anticipate.

This is basic scientific research, but scientists expect it to have multiple research and industrial applications. “This system can be used to study a variety of physical phenomena that are otherwise inaccessible,” says Professor Kaminer. “We are planning experiments to measure optical vortices, chaos theory experiments, and simulations of phenomena that occur near black holes. In addition, our findings are placed in electrical circuits. It has the potential to enable the production of atomically thin optical fiber “cables” that can transmit data without overheating the system. This is a task that is currently facing considerable challenges due to circuit minimization. “

Yaniv Kurman and Ido Kaminer

LR: Yaniv Kurman and Professor Ido Kaminer.Credit: Technion-Israel Institute of Technology

The team’s work begins to study optical pulses within a new set of materials, expanding the capabilities of electron microscopy and promoting the possibility of optical communication through an atomically thin layer.

“I was excited about these discoveries,” said Professor Harald Giessen of the University of Stuttgart, who was not part of the study. “This shows a true breakthrough in ultra-fast nanooptics, State-of-the-art And that State-of-the-art Of the scientific frontier. Real-space and real-time observations are beautiful and, to my knowledge, have never been proven. “

Another prominent scientist not involved in this study, John Joanopros of the Massachusetts Institute of Technology, added: “The key to this achievement lies in the ingenious design and development of the experimental system. This work by Ido Kaminer and his group and colleagues is an important step forward. It is of great scientific and technical interest. Yes, it’s very important for this area. “

Professor Kaminer is also affiliated with the Helen Diller Quantum Center and the Russell Berrie Nanotechnology Institute. This study was led by a PhD. Students Yaniv Kurman and Raphael Dahan. Other members of the research team were Dr. Kangpeng Wang, Michael Yannai, Yuval Adiv, and Ori Reinhardt. This study is based on international collaboration with a group of Professor James Edgar (Kansas State University), Professor Mathieu Kociak (Université Paris Sud), and Professor Frank Koppens (ICFO, Barcelona Institute of Science and Technology).

Reference: “Spatiotemporal Imaging of 2D Polariton Wave Packet Dynamics Using Free Electrons” Yaniv Kurman, Raphael Dahan, Hanan Herzig Sheinfux, Kangpeng Wang, Michael Yannai, Yuval Adiv, Ori Reinhardt, Luiz HG Tizei, Steffi Y. Woo, Jiahan Li , James H. Edgar, Mathieu Kociak, Frank HL Koppens, Ido Kaminer, June 11, 2021 Science..
DOI: 10.1126 / science.abg9015

Researchers observe sound and light pulses in 2D materials for the first time Researchers observe sound and light pulses in 2D materials for the first time

Back to top button