Twisted Trilayer Graphene

Artist rendition of twisted trilayer graphene. Credit score: Polina Shmatkova & Margarita Davydova

In 2018, the physics world was set ablaze with the invention that when an ultrathin layer of carbon, known as graphene, is stacked and twisted to a “magic angle,” that new double layered construction converts right into a superconductor, permitting electrical energy to circulate with out resistance or vitality waste. Now, in a literal twist, Harvard scientists have expanded on that superconducting system by including a 3rd layer and rotating it, opening the door for continued developments in graphene-based superconductivity.

The work is described in a brand new paper in Science and may someday assist lead towards superconductors that function at increased and even near room temperature. These superconductors are thought of the holy grail of condensed matter physics since they’d enable for great technological revolutions in lots of areas together with electrical energy transmission, transportation, and quantum computing. Most superconductors at present, together with the double layered graphene construction, work solely at ultracold temperatures.

“Superconductivity in twisted graphene supplies physicists with an experimentally controllable and theoretically accessible mannequin system the place they will play with the system’s properties to decode the secrets and techniques of excessive temperature superconductivity,” stated one of many paper’s co-lead authors Andrew Zimmerman, a postdoctoral researcher in working within the lab of Harvard physicist Philip Kim.

Graphene is a one-atom-thick layer of carbon atoms that’s 200 instances stronger than metal but is extraordinarily versatile and lighter than paper. It has nearly all the time been recognized to be an excellent conductor of warmth and electrical present however is notoriously tough to deal with. Experiments unlocking the puzzle of twisted bilayer graphene have been ongoing since MIT physicist Pablo Jarillo-Herrero and his group pioneered the rising subject of “twistronics” with their experiment in 2018 the place they produced the graphene superconductor by twisting it to a magic angle of 1.1 levels.

The Harvard scientists report efficiently stacking three sheets of graphene after which twisting every of them at that magic angle to supply a three-layered construction that isn’t solely able to superconductivity however does so extra robustly and at increased temperatures than lots of the double-stacked graphene. The brand new and improved system can also be delicate to an externally utilized electrical subject that permits them to tune the extent of superconductivity by adjusting the energy of that subject.

“It enabled us to look at the superconductor in a brand new dimension and offered us with vital clues concerning the mechanism that’s driving the superconductivity,” stated the examine’s different lead creator Zeyu Hao, a Ph.D. pupil within the Graduate College of Arts and Sciences additionally working within the Kim Group.

A kind of mechanisms has the theorists actually excited. The trilayer system confirmed proof that its superconductivity is because of robust interactions between electrons versus weak ones. If true, this can’t solely assist open a path to excessive temperature superconductivity however doable purposes in quantum computing.

“In most standard superconductors, electrons transfer with a excessive pace and infrequently cross-paths and affect one another. On this case, we are saying their interplay results are weak,” stated Eslam Khalaf, a co-author on the examine and postdoctoral fellow working within the lab of Harvard physics professor Ashvin Vishwanath. “Whereas weakly interacting superconductors are fragile and lose superconductivity when heated to a couple Kelvins, robust coupling superconductors are rather more resilient however a lot much less understood. Realizing robust coupling superconductivity in a easy and tunable system akin to trilayer may pave the way in which to lastly develop a theoretical understanding of strongly-coupled superconductors to assist notice the purpose of a excessive temperature, perhaps even room temperature, superconductor.”

The researchers plan on persevering with to discover the character of this uncommon superconductivity in additional research.

“The extra we perceive, the higher we now have likelihood to extend the superconducting transition temperatures,” stated Kim.

Reference: 4 February 2021, Science.

Funding: Nationwide science basis, Division of Protection, Simons Collaboration on Extremely-Quantum Matter

By Rana

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