A discovery six years in the past took the condensed-matter physics world by storm: Extremely-thin carbon stacked in two barely askew layers grew to become a superconductor, and altering the twist angle between layers might toggle their electrical properties. The landmark 2018 paper describing “magic-angle graphene superlattices” launched a brand new area referred to as “twistronics,” and the primary creator was then-MIT graduate pupil and up to date Harvard Junior Fellow Yuan Cao.
Along with Harvard physicists Amir Yacoby, Eric Mazur, and others, Cao and colleagues have constructed on that foundational work, smoothing a path for extra twistronics science by inventing a neater solution to twist and examine many kinds of supplies.
A brand new paper in Nature describes the group’s fingernail-sized machine that may twist skinny supplies at will, changing the necessity to fabricate twisted gadgets one after the other. Skinny, 2D supplies with properties that may be studied and manipulated simply have immense implications for higher-performance transistors, optical gadgets akin to photo voltaic cells, and quantum computer systems, amongst different issues.
“This improvement makes twisting as straightforward as controlling the electron density of 2D supplies,” mentioned Yacoby, Harvard professor of physics and utilized physics. “Controlling density has been the first knob for locating new phases of matter in low-dimensional matter, and now, we are able to management each density and twist angle, opening limitless prospects for discovery.”
Cao first made twisted bilayer graphene as a graduate pupil within the lab of MIT’s Pablo Jarillo-Herrero. Thrilling because it was, the achievement was tempered by challenges with replicating the precise twisting.
On the time, every twisted system was exhausting to supply, and consequently, distinctive and time-consuming, Cao defined. To do science with these gadgets, they wanted tens and even tons of of them. They puzzled if they may make “one system to twist all of them,” Cao mentioned — a micromachine that might twist two layers of fabric at will, eliminating the necessity for tons of of distinctive samples. They name their new system a MEMS (micro-electromechanical system)-based generic actuation platform for 2D supplies, or MEGA2D for brief.
The Yacoby and Mazur labs collaborated on the design of this new software equipment, which is generalizable to graphene and different supplies.
“By having this new ‘knob’ by way of our MEGA2D know-how, we envision that many underlying puzzles in twisted graphene and different supplies could possibly be resolved in a breeze,” mentioned Cao, now an assistant professor at College of California Berkeley. “It can definitely additionally convey different new discoveries alongside the best way.”
Within the paper, the researchers demonstrated the utility of their system with two items of hexagonal boron nitride, a detailed relative of graphene. They had been capable of examine the bilayer system’s optical properties, discovering proof of quasiparticles with coveted topological properties.
The convenience of their new system opens a number of scientific roadways, for instance, using hexagonal boron nitride twistronics to supply mild sources that can be utilized for low-loss optical communication.
“We hope that our strategy shall be adopted by many different researchers on this affluent area, and all can profit from these new capabilities,” Cao mentioned.
The paper’s first creator is nanoscience and optics skilled Haoning Tang, a postdoctoral researcher in Mazur’s lab and a Harvard Quantum Initiative fellow, who famous that growing the MEGA2D know-how was a protracted means of trial and error.
“We did not know a lot about methods to management the interfaces of 2D supplies in actual time, and the present strategies simply weren’t reducing it,” she mentioned. “After spending numerous hours within the cleanroom and refining the MEMS design — regardless of many failed makes an attempt — we lastly discovered the working answer after a couple of 12 months of experiments.” All nanofabrication befell at Harvard’s Middle for Nanoscale Techniques, the place employees offered invaluable technical assist, Tang added.
“The nanofabrication of a tool combining MEMS know-how with a bilayer construction is a veritable tour de drive,” mentioned Mazur, the Balkanski Professor of Physics and Utilized Physics. “Having the ability to tune the nonlinear response of the ensuing system opens the door to a complete new class of gadgets in optics and photonics.”