MIT Turns “Magic” Superconducting Material Into Versatile Electronic Devices


An artistic representation of the nanoscale structure of one of the new MIT nanodevices. The two twisted sheets of graphene are represented by the metallic blue carbon atoms of the honeycomb lattice. The upper and lower electrodes (gates) of graphene are represented by gold. The electrons are represented by small light blue circles. Credit: Image courtesy of Ella Maru Studio

Work on three GrapheneDevices based on may provide new insights into superconductivity.

MIT Researchers and colleagues have transformed “magical” materials, which consist of a thin layer of carbon atoms, into three useful electronic devices. Usually, such devices are all the keys to the quantum electronics industry and are made using a variety of materials that require multiple manufacturing processes. MIT’s approach automatically solves a variety of problems associated with these more complex processes.

As a result, this research has the potential to usher in a new generation of quantum electronic devices for applications such as: Quantum computingIn addition, the device can conduct electricity, either superconducting or without resistance. However, they do it through unconventional mechanisms, and further research may provide new insights into superconducting physics.Researchers in the May 3, 2021 issue Nature nanotechnology..

“This study demonstrated that magic angle graphene is the most versatile of all superconducting materials, enabling multiple quantum electronic devices to be realized in a single system using this advanced platform. This allowed us to explore for the first time new superconducting physics that emerged only in two dimensions, “said Pablo Jaliro Herrero, MIT professor of green physics and leader of the study. I am. Jarillo-Herrero is also a member of MIT’s Materials Laboratory.

Magic angle

The new “magical” material is based on graphene, a single layer of carbon atoms arranged in a hexagon that resembles a honeycomb structure. Since the first clear separation of graphene in 2004, interest in this material has skyrocketed due to its unique properties. For example, it is stronger, more transparent, and more flexible than diamond. It also easily conducts both heat and electricity.

In 2018, the Jarillo-Herrero group Amazing discoveries There are two layers of graphene, one on top of the other. However, these layers did not exactly overlap each other. Rather, it rotated slightly at a “magic angle” of 1.1 degrees.

Daniel Rodin Reglen

Daniel Rodin-Reglen, a graduate student at the Massachusetts Institute of Technology (MIT), lists the chip carriers used to develop new graphene-based electronic devices. He stands next to a diluting refrigerator similar to the one used in the work. Credits: Bharath Kannan

The resulting structure allowed graphene to be either a superconductor or an insulator (which blocks the flow of current), depending on the number of electrons in the system provided by the electric field. In essence, the team was able to adjust the graphene to a completely different state by simply turning the knob and changing the voltage.

The overall “magical” material, formally known as the Magic Angle Twist Double-Layer Graphene (MATBG), has generated a great deal of interest in the research community and may even stimulate a new field known as Twistronics. It is also the center of my current job.

In 2018, Jarillo-Herrero and his colleagues changed the voltage supplied to the magical material through a single electrode or metal gate. In the current study, “we introduced multiple gates to expose different areas of the material to different electric fields,” said Daniel Rodin-Reglen, a graduate student in physics and lead author of the treatise. I will. Nature nanotechnology paper.

Suddenly, the team was able to adjust different sections of the same magical material to a large amount of electronic state, from superconductivity to insulation, and somewhere in between. Then, by applying gates of different configurations, it was possible to reproduce all the parts of an electronic circuit, which are usually made of completely different materials.

Working equipment

Ultimately, the team used this approach to create three different working quantum electronic devices. These devices include Josephson junctions, or superconducting switches. The Josephson junction is a component of the qubit behind a superconducting quantum computer. It also has a variety of uses, such as incorporating it into a device that can measure magnetic fields very accurately.

The team also created two related devices: a spectroscopic tunneling device and a single-electron transistor, or a very sensitive device for controlling the movement of electricity, literally one electron at a time. The former is the key to studying superconductivity, and the latter is very sensitive to electric fields, so it has a variety of uses.

All three devices have the advantage of being made of a single electrically adjustable material. Traditionally, those made of multiple materials face a variety of challenges. For example, different materials may not be compatible. “If you’re dealing with one material right now, those problems will be solved,” says Rodan-Legrain.

William Oliver, associate professor of electrical engineering and computer science at MIT, said: Apply voltage to the nearby gate. In this work, Rodan-Legrain et al. They have shown that MATBG’s single-flake electrical gates can create fairly complex devices that include superconducting regions, normal regions, and isolated regions. The traditional approach is to manufacture the device in several steps using different materials. With MATBG, you can completely reconfigure the resulting device by simply changing the gate voltage. “

To the future

Works listed in Nature nanotechnology Paper paves the way for many potential future advances. For example, Rodan-Legrain states that it can be used to create the first voltage-adjustable qubit from a single material and apply it to future quantum computers.

In addition, the new system allows for a more detailed study of MATBG’s mysterious superconductivity and is relatively manageable, so the team hopes to provide insight into the creation of high-temperature superconductors. Superconductors only operate at very low temperatures. “It’s actually one of the big hopes. [behind our magic material]”Rodan-Legrain says. To better understand its hot cousin, “Can it be used as a kind of Rosetta Stone?”

To get a glimpse of how science works, Rodan-Legrain describes the surprises the team encountered while conducting research. For example, some of the data from the experiment did not meet the team’s initial expectations. This is because the Josephson junction created using the atomically thin MATGB is two-dimensional and behaves significantly differently from its traditional 3D counterpart. “It was great that the data was provided, confused by it, and deepened and understood.”

See also: “Highly Adjustable Junctions and Nonlocal Josephson Effects in Magic Angle Graphene Tunneling Devices” Daniel Rodin-Reglen, Yuan Kao, John Min Park, Sergio C. Dela Valera, Marica T. Randelia, Kenji Watanabe, Takashi Taniguchi and Pablo Jaliro Herrero, May 3, 2021, Nature nanotechnology..
DOI: 10.1038 / s41565-021-00894-4

In addition to Jarillo-Herrero and Rodan-Legrain, the additional author of this treatise is Yuan Cao, a postdoctoral fellow at the Materials Research Institute (MRL) at MIT. Park Jung Min, a graduate student in the Department of Chemistry. Sergio C. de la Barrera, a postdoc of MRL. Malika T. Randeria, Postdoctoral Fellow, Department of Physics. Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science. (Rodan-Legrain, Cao, and Park were equal contributors to this treatise.)

This work is from the National Science Foundation, US Department of Energy, US Army Research Bureau, Fundació Bancaria “la Caixa”, Gordon and Betty Moore Foundation, Fundación Ramon Areces, MIT Paparald Fellowship, and Japanese Ministry of Education, Culture, Sports, Science and Technology.

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