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MIT Researchers Gear Up for Center for Integrated Quantum Materials

Eight investigators will focus on new materials, processes for quantum computing.


Groundbreaking work uncovering unexpected electronic behavior in graphene is a natural segue to MIT Physics Professor Raymond C. Ashoori’s new role as a co-principal investigator of the NSF-funded Center for Integrated Quantum Materials.

A recent NSF-sponsored gathering at Harvard brought together CIQM participants for a brainstorming exercise. “I was really impressed with the range of ideas that came up and possibilities that people were cooking up that I don’t think that anyone had ever thought of before because we were getting people from different backgrounds who have a mission of working together. We don’t know how those things will go, but I could see there was a lot of value in the exercise. Follow-through, of course, is going to be key,” Ashoori says.

“The thing that’s nice about it is that we have eight people here at MIT being sponsored by it,” Ashoori says. “We’re all thinking about very similar kinds of problems. It’s a pretty tight fit. I’m really happy to have an excuse to hang out with all these people and for us to get together more regularly. It’s a group where everyone in it fits very naturally.”

The multi-site Center for Integrated Quantum Materials, a five-year, National Science Foundation-funded project, is led by Robert M. Westervelt, Mallinckrodt Professor of Applied Physics and of Physics, at Harvard University. There are two other co-principal investigators at Howard University in Washington, D.C., and the Museum of Science in Boston.

Gap-in-Graphene
By stacking graphene on a similarly patterned layer of boron nitride, MIT researchers found interactions between carbon and boron atoms on one sublattice and carbon and nitrogen atoms on the other resulted in adequate breaking of the sublattice symmetry to give the electrons an observable mass. In the above illustration, adjacent atoms are referred to as A sites and B sites. Illustration used with permission of Michael Fuhrer, Monash University.


Ashoori’s lab group at MIT recently demonstrated a unique bandgap in graphene coupled to hexagonal boron nitride that could be a precursor to developing the material for functional transistors. Subsequent research showed magnetic fields applied in the graphene plane forced electrons at the edge of graphene to move in opposite directions based on their spins. (See related story.)

Building on earlier work with edge magneto-plasmons (charged excitations at the edge of a sample that move in a particular direction depending on the sign of the charge carriers and the magnetic field), Ashoori plans to study edge magneto-plasmons in graphene. “A little charge sensor placed near the graphene should be able to detect the magneto-plasmons going around and around,” he says.

“In graphene, the situation is I think going to be pretty interesting because you can change the carriers from being real electrons (expected to travel in one direction) or real holes (expected to travel in the other direction) and then there is an in-between region where the magneto-plasmons might travel in either direction. We really don’t know exactly what they are going to do, so I think it’s just a fun region to explore,” Ashoori explains.

The typical experimental sample size for graphene of just a few microns is too small for the edge plasmon work Ashoori plans.  “The plasmons would travel too fast, and we wouldn’t really be able to time them going around and around or to watch them in detail,” Ashoori says. So he is collaborating with Jing Kong, the ITT Career Development Associate Professor of Electrical Engineering at MIT, to grow much larger pieces of graphene using chemical vapor deposition (CVD) techniques that Kong pioneered, and with Electrical and Computer Engineering Professor Gary Harris at Howard University, who also grows large area graphene sheets.

The center will provide enough funds for each faculty member to support one graduate student or postdoctoral associate a year, with additional discretionary funds for equipment. The MIT award will be managed by the Materials Processing Center.

Besides Ashoori, the MIT faculty participating in the Center for Integrated Quantum Materials are: Physics faculty Pablo Jarillo-Herrero, Nuh Gedik, Liang Fu, Leonid S. Levitov and Jagadeesh Moodera (senior scientist); and Electrical Engineering and Computer Science  faculty Tomas Palacios and Jing Kong.

– Written by Denis Paiste, Materials Processing Center

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Related websites

Center for Integrated Quantum Materials

Museum of Science

 

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