Atoms do strange things when pushed out of their comfort zone. Rice University engineers have come up with a new way to give them a boost.
Materials theorist Boris Yakobson and his team at Rice’s George R. Brown School of Engineering have a theory that altering the outline of a layer of 2D material, thereby altering the relationships between its atoms, might be easier to do. than previously thought.
While others twist 2D bilayers – two stacked layers – of graphene and the like to change their topology, Rice researchers suggest, through computer models, that growing or stamping 2D single-layer materials on a corrugated surface carefully designed would achieve “an unprecedented effect”. level of control” over their magnetic and electronic properties.
They say the discovery opens a way to explore many-body effects, the interactions between multiple microscopic particles, including quantum systems.
The paper by Yakobson and two former students, co-lead authors Sunny Gupta and Henry Yu, from his lab appears in Communication Nature.
The researchers were inspired by recent findings that twisting or deforming bilayers of 2D materials like bilayer graphene into “magic angles” induces interesting electronic and magnetic phenomena, including superconductivity.
Their models show that instead of twisting, simply stamping or growing a 2D material like hexagonal boron nitride (hBN) on a bumpy surface naturally strains the material’s lattice, allowing it to form fields. pseudo-electric and pseudo-magnetic and possibly to produce rich physical effects. similar to those found in twisted materials.
Flat hBN is an insulator, but the researchers found that straining the atoms in their model created band structures, making it a semiconductor.
The advantage of their strategy, Gupta said, is that the deformation would be highly controllable through surface bumps because the substrates could be precisely patterned using electron beam lithography. “It will also allow controlled change of electronic states and quantum effects by designing substrates with different topography,” he said.
Because charge can be manipulated to flow in one direction, the path it follows is a model for 1D systems. Yakobson said this can be used to explore properties of 1D quantum systems that are not accessible through twisted graphene.
“Imagine a single-lane road such that cars are only allowed to move in one direction,” Gupta said. “A car cannot pass the one in front of it, so traffic will only move when all the cars are moving collectively.
“That’s not the case in 2D or when you have multiple lanes, where cars — or electrons — can pass,” he said. “Like cars, electrons in a 1D system will flow collectively, not individually. It makes 1D systems special with rich and unexplored physics. »
Gupta said it would be much easier to form a bumpy substrate with an electron beam than it is now to twist 2D bilayers of graphene or other heterostructures like hBN to less than one degree of precision.
“In addition, one can realize 1D quantum states, which are usually not accessible by twisting 2D bilayers,” he said. “This will explore 1D physical effects that have remained largely elusive until now. »
Yakobson is the Karl F. Hasselmann Professor of Engineering and Professor of Materials Science, Nanoengineering, and Chemistry.
The US Army Research Office (W911NF-16-1-0255) and the Office of Naval Research (N00014-18-1-2182) supported the research. Computing resources were provided by the National Science Foundation’s XSEDE facility.
Source of the story:
Materials provided by rice university. Original écrit par Mike Williams. Note: Content may be edited for style and length.