The Magic of Rotated Graphene Sheets


Interview | MCQST community

Dmitri Efetov was recently appointed Professor of Solid State Physics at LMU. Learn more about his work with 2D materials, and how it brought him to Munich.

Dmitri Efetov: The Magic of Rotated Graphene Sheets

Two ultra-thin carbon sheets, placed on top of each other and rotated at the magic angle of 1.1 degrees, give rise to very exotic materials properties with very exotic physical properties. The 2D material almost magically becomes a superconductor – among other things. This discovery triggered an incredible hype in physics. Among the key players who have devoted themselves to the unconventional behavior of graphene sheets is Dmitri Efetov. He has been Professor of Solid State Physics at Ludwig-Maximilians-Universität (LMU) since August 2021.

It might be said that Efetov’s career as a physicist was determined from birth; after all, his father was a physics professor before him. But unlike his father, Dmitri Efetov, who was born in Moscow and grew up in Stuttgart and Bochum, did not take the path of a theoretician. Instead, he has spent a considerable amount of time experimenting on the two-layer carbon films.

The budding physicist completed his studies at the Swiss Federal Institute of Technology (ETH) in Zurich. Even before completing his diploma thesis, Efetov moved to the USA. He wanted to spend a year at Columbia University in New York. That he would end up staying in the USA for much longer was neither planned nor foreseeable at the beginning. This was partly because graphene was discovered in England just two years before the ETH student arrived in the USA. And at Columbia University, Prof. Philip Kim's group was at the forefront of research with the novel material, which displayed remarkable properties. The dimensions and possibilities that these carbon atoms, arranged in a honeycomb structure, would open up – in research and for the young physicist – were certainly not foreseeable at the time. "I stumbled onto it rather by chance, although I was already aware that it was something new, something exciting”, explains Efetov.

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Inexhaustible potential and pure exoticism

Fascinated by these materials, it was only logical for the young scientist to devote his doctoral thesis to graphene as well. His dissertation addressed the question of whether this 2D carbon could be superconducting. This was rather a marginal topic and many researchers considered it exotic and even categorized it as rather unrealistic. Efetov then spent several years developing ideas for inducing superconductivity in graphene layers. The original idea was that the ultra-thin graphene layers could form an intrinsic superconductor. Although his experiments did not lead to the discovery he wanted, they opened up many new insights, and have since paved the way to three patents. It therefore sounds a bit like excessive modesty, when the scientist declares that patents are more of a by-product. His research had not been aimed at discovering patents and possible applications relating to this unconventional material. However, the researchers found out that graphene can be used as a transistor. To achieve superconductivity in graphene and generate results for his doctoral thesis, Efetov finally used a trick: he brought graphene into contact with a known superconductor. With that, the properties of the superconductor were transferred to the graphene.

Quantum detectors and magic graphene

Dmitri Efetov then branched out into somewhat different subject areas during his time as a postdoc at the Massachusetts Institute of Technology (MIT). However, there were points of contact in Dirk Englund's group, which specialized in quantum information: there too, research was carried out with graphene, specifically to develop quantum detectors. And it was in fact the postdoc from Europe who finally succeeded in building such a single-photon detector. And so Efetov was also offered a group leadership position at the Institut de Ciències Fotòniques (ICFO) in Barcelona very early in his postdoc phase. This came as a surprise to him, especially as he expected to stay in the USA. But the conditions for the move to Barcelona were very favorable and, having collaborated with them, Dmitri Efetov already knew some of the researchers there.

At ICFO, he set up a group to continue working on the detectors. Shortly after he started his research in Barcelona, one of his former colleagues from Columbia University discovered that graphene is superconducting after all, and exhibits very unique properties at that. Of course, he had to follow up on this astonishing discovery. His team – the third group worldwide to do so—was finally able to reproduce the superconductivity of graphene. Moreover, they managed to discover even more phases. “Since then, we have been one of the key groups in this field", confirms Efetov. From then on, his group not only worked on quantum detectors, but also developed detectors from the “magical” graphene.

Phase diversity and research

And because the Russian-German physicist's field of research fits perfectly with the goals of the quantum researchers in Munich, it seems logical that Efetov's team will soon be located on the Isar. The relocation of the working group is expected to be largely completed in the summer of 2022.

The solid-state physicist is looking forward to his move to Munich. For one thing, he sees many opportunities for collaboration with groups that are also working on correlated states and superconductors and are also part of the MCQST network. Efetov already knows many of these researchers in Munich and is looking forward to the many opportunities for collaboration that could arise. In any case, the ultra-thin two-dimensional carbon layers, which consist of a whole zoo of phases, as Dmitri Efetov explains, open up a great many possibilities for working together with other groups. Secondly, he is pleased at the prospect of teaching and conducting research in Munich because there are a lot of very good physics students at LMU and TUM.

However, before the graphene expert starts pursuing his various research projects on the Isar, Efetov has another project first and foremost on his mind: raising his newborn baby.

About Dmitri Efetov

Dmitri has been Professor of Solid State Physics at LMU in Munich since August 2021.

While studying physics at ETH in Zurich, Efetov transferred to Columbia University, New York City (USA), where he was already working with graphene under Prof. Philip Kim for his diploma thesis.

From 2007 to 2014, he conducted research in Prof. Philip Kim’s group at Columbia University (New York City, USA) and completed his doctorate on the superconductivity of graphene ("Towards inducing superconductivity into graphene").

From 2014 onwards, Efetov worked as a postdoc on quantum detectors, among other things, in Prof. Dirk Englund's group at MIT (USA).

In 2017 he received an invitation to ICFO in Barcelona, to continue his research on detectors there, with a new group. His team belonged to the first group to reproduce superconductivity in graphene.

In August 2021, Dmitri Efetov was appointed Professor of Solid State Physics at LMU.

Efetov has received several scholarships and prizes, such as the Charles H. Towns Award for his outstanding research achievements during his PhD, the Obra Social ”laCaixa” Junior Leader Fellowship, an ERC Starting Grant and was a finalist of the LaVanguardia Science Prize, for his ground-breaking discovery of new states in “magic” angle graphene. He is the also leader of the 2D-SIPC project in the EUs Quantum Technology Flagship, as well as a member of its Science and Engineering board. In Munich he is a Core-Member of the Munich Center of Quantum Science and Technology and Head of the new LMU Quantum Technology Park Cleanroom within the Munich Quantum Valley initiative.

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