Atoms do weird things when they are pushed out of their comfort zone. Rice University engineers have devised a new way to give them a boost.
Materials theorist Boris Jakobson and his team at the George R. Brown School of Engineering in Rice have theorized that changing the outlines of a layer of two-dimensional matter, and thus changing the relationships between its atoms, may be easier than previously thought.
While others warp 2D layers — two stacked layers — of graphene and the like to alter their topology, the Rice researchers suggest, through computer models, that growing or sealing single-layer 2D materials on a carefully designed corrugated surface would achieve an “unique effect.” preceded by”. level of control” over their magnetic and electronic properties.
They say this discovery opens the way for the exploration of multiple body effects, and the interactions between multiple microscopic particles, including quantum systems.
The paper by Jakobson and two former students, co-authors Sunny Gupta and Henry Yu, from his lab appears in nature of communication.
The researchers were inspired by recent findings that twisting or distorting the bilayers of two-dimensional materials such as bilayer graphene into “magic angles” leads to interesting electronic and magnetic phenomena, including superconductivity.
Their models show that instead of warping, simply stamping or growing a 2D material such as hexagonal boron nitride (hBN) on a bumpy surface naturally strains the material’s lattice, allowing it to form fields. physical effects. Similar to that of the twisted material.
Flat hBN is an insulator, but the researchers found that stressing the atoms in their model creates stripe structures, making them semiconductors.
The advantage of their strategy, Gupta said, is that the deformation is highly controllable by surface protrusions because the substrates can be precisely shaped using electron beam lithography. “It will also allow for the controlled alteration of electronic states and quantum effects by designing substrates with different topography,” he said.
Since the charge can be manipulated to flow in one direction, the path it follows is a template for 1D systems. This can be used to explore the properties of one-dimensional quantum systems that cannot be accessed by twisted graphene, Jakobson said.
“Imagine a single-lane road where cars are only allowed to move in one direction,” Gupta said. “The car cannot overtake the car in front of it, so the traffic will only move when all the cars are moving en masse.
“This is 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 for the rich and unexplored physics.”
It would be much easier to make a rugged substrate using an electron beam than it would be to twist 2D layers of graphene or other heterogeneous structures like hBN to less than one degree of resolution, Gupta said.
“In addition, one can achieve one-dimensional quantum states, which are not normally accessible by twisting the two-dimensional layers,” he said. This will explore one-dimensional physical effects that have remained largely elusive until now. »
Jakobson is the Carl F. Haselman Engineering and Professor of Materials Science, Nanoengineering, and Chemistry.
The US Army Research Office (W911NF-16-1-0255) and the Naval Research Office (N00014-18-1-2182) supported the research. Computing resources were provided by the National Science Foundation’s XSEDE Facility.
Material provided by rice university. Original by Mike Williams. Note: Content can be modified according to style and length.
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