Rafi Bistritzer, Wolf Prize Winners in Physics: I knew the work I did with MacDonald was making a buzz, but I didn't know how much

"I finished my doctorate at the Weizmann Institute and then went on to do a post-doctorate with Prof. MacDonald in Austin, Texas. As part of the research, we published several articles on the rotated bilayer graphene. One of them particularly influenced the field of nanotechnology"

The text This morning the names of the winners of the 2020 Wolf Prize for Science and Art were announced at the Mishkan of the Presidents of Israel, in the presence of President Reuven (Rubi) Rivlin, Minister of Education Rabbi Rafi Peretz and Nobel laureate Prof. Dan Shechtman.
The Wolf Prize in Physics will be awarded this year to three winners: Prof. Pablo Jarillo-Herrero, born in Spain, who serves as a professor at the Massachusetts Institute of Technology - (MIT) USA, Prof. Alan H. McDonald from the University of Texas at Austin - and Dr. Rafi Bistritzer, from Applied Materials - Israel, for their pioneering work in the theory and experiment of twisted two-layer graphene that will lead, among other things, to a tremendous energy revolution.

The Wolff Prize is the most prestigious scientific prize distributed in Israel, many of its winners in fields that overlap with the Nobel Prize have subsequently also won the prestigious world prize, including Prof. Dan Shechtman and the 2019 Nobel Prize winners in Physics, Michel Mayor and Didia Colo, discoverers of the first planet outside the solar system , who received the Wolf Prize for the same discovery in 2017.

In a conversation with CHIPORTAL, Dr. Bistritzer says that he was surprised. "I finished my doctorate at the Weizmann Institute and then went on to do a post-doctorate with Prof. MacDonald in Austin, Texas. As part of the research, we published several articles on the rotated bilayer graphene. One of them echoed. I have already left the field and have not been involved in theoretical physics for a decade. I am still in contact with my supervisor at the time, Alan McDonald and he informed me that the work is mentioned in many articles. When we published the work, in which we explained how to perform the process more easily, we knew that there would be experimenters who would ask to perform such experiments. "It's a difficult award to receive, so it's a big surprise." Dr. Bistritzer explains.

What is the importance of the discovery?

Prof. Bistritzer: "There are many phases - states of matter that are known to exist experimentally but cannot be explained. This has been tried for decades, but the experiments that the animal has to do in order to record them are complicated, for example coppers that are on high temperature conductors - conductors without fusion. There are many theories that try to explain this, and the understanding has greatly improved, but there is no complete understanding of the material's behavior. Experiments with this material are very difficult, which this system allows with a simple operation similar to that performed by a gate gate in a transistor to change the voltage of the rotated graphene and make it possible to switch between an isolated state and a state on a conductor."

"Now it is easy to investigate the system and try to understand why this material is on a conductor. There are fantasies about things that could be done if it were used for switching transistors, but another vision for another time. But already now the method allows scientists in the world to investigate conductivity and insulation in a controlled and relatively easy way."
"This is a very interesting physical phenomenon. A prize is not given for the phenomenon alone, but because of the potential inherent in it to learn new physics.
How did you get to Applied and what is your role in the company?

"After the post I returned to Israel, I looked for a position in the academy but it didn't work out. McDonald's wanted me to stay in the US but I didn't want to. Then I moved to industry. The truth is that we do interesting things and try to solve problems that no one in the world can solve. And I have an excellent group of excellent people."

"At Applied, I manage a group of algorithms and deal with the development of an electronic scanner. I can't say too much, only to say that we develop algorithms related to detection and metrology and use methods of artificial vision and machine learning.
In the chip industry, the challenge of electron microscopes has greatly increased because everything is getting smaller and with optical means it is impossible to discover everything, and there really is a great challenge in the things that can be done with an electron microscope to advance the industry in the advanced production nodes."

Reasons of the award committee

In 2004, a two-dimensional layer with a thickness of one carbon atom called "graphene" was isolated for the first time. Since then, the interest in such layers and two-dimensional materials has been increasing, and graphene forms the basis for a completely new generation of materials and technologies. The hope is that applications based on graphene will benefit the environment and reduce costs.

In the electronics and computer industry, materials whose conductivity can be controlled are required. Groundbreaking studies by the researchers Jarillo Herrero, Macdonald and Bistritzer showed that the conduction properties of graphene junctions can be controlled by the spatial angle between the graphene layers and that at certain angles there is a surprising physical behavior of the electrons. In 2011, the group of Alan MacDonald, a theoretical physicist from the University of Texas, studied an interesting behavior of twisted two-layer graphene plates placed on top of each other, that is, in a situation where there is a certain, small angle between the plates. According to the calculations of Macdonald and Bistritzer (who worked as a postdoctoral student with Macdonald at the time). The tunneling speed of electrons between the layers depends on the angle of rotation between them and disappears completely at a "magic angle" of 1.1 degrees. The hope was that this would lead to the creation of a new superconductor, i.e. a material which allows the passage of electric current without resistance at all and without energy losses.

The original article by Macdonald and Bistritzer that described their discovery did not receive a sympathetic response in the scientific world and was even forgotten for several years. At that time, Prof. Grillo-Harari was working on twisted bilayer graphene in his laboratory at the Massachusetts Institute of Technology. He became convinced that MacDonald and Bistritzer's ideas had merit and his research group put a lot of effort into creating and measuring bilayer graphene twisted at different angles.
The experiments bore fruit when it was found that placing the layers at an angle of 1.1 degrees relative to one another, an angle known as the "magic angle", results in extraordinary electrical properties, just as suggested by MacDonald and Bistritzer. In this situation, at extremely low temperatures, the electrons move from layer to layer with high efficiency and create a lattice with extraordinary properties. These findings were published in a 2018 article, which was a real revolution in the field of physics, and caused a flood of additional works in the field of bilayer graphene. Pablo Jarrillo-Herrero Massachusetts Institute of Technology Alan McDonald University of Texas, Austin The new discovery makes it possible to build a superconductor from two-layer graphene in which the movement of electrons is completely controlled by an external electric voltage. Such electrical behavior is reminiscent of the behavior of a family of copper-based superconducting materials called cuprates. The cuprates show electrical conduction without resistance at extremely high temperatures compared to other superconductors. As a result, cuprates have become a great source of hope for realizing the dream of conducting electricity without energy loss at temperatures close to room temperature.
If the goal is achieved, it will be a tremendous energy revolution. However, one of the obstacles preventing such a revolution is that we currently do not have a theory that explains the behavior of superconductors at high temperatures, and in the absence of a solid theoretical basis it is difficult to develop new and better materials. This is one of the reasons for the great excitement surrounding the discovery of bilayer graphene and the magic angle between the layers, a discovery that allows for a better understanding of what happens at the microscopic level during the transition from a state of a conductor to a state of a superconductor.