TALLAHASSEE, Fla. – Researchers from Columbia University working at the National High Magnetic Field Laboratory (MagLab) have observed a physical phenomenon in bilayer graphene that could usher in a new generation of quantum computers. Their results are published today in the journal Science.
Graphene is a material that holds tremendous promise in revolutionizing computers, batteries, cell phones, televisions and even airplanes. A one-atom thick, honeycomb array of carbon atoms, graphene is virtually see-through, yet 300 times stronger than steel and 1,000 times more conducting than silicon.
Researchers have been working with graphene at the MagLab for nearly a decade, said Tim Murphy, Director of the MagLab’s DC Field Facility.
“We are excited to play such a critical role in the exploration of this emergent material,” said Murphy. “As a user facility, we're pleased to provide the combination of high magnetic fields and low temperatures not available at Columbia University, yet needed to pursue this area of work by truly outstanding researchers.”
The fractional quantum Hall state, a collective behavior where thousands of individual electrons behave as a single system, was initially discovered in single layer graphene in 2009. This new research, however, reveals the same effect in bilayer graphene, or two sheets of the material stacked together.
Using a breakthrough fabrication technique developed through the combined efforts of Columbia University researchers from Mechanical Engineering, Electrical Engineering and Physics, the team was able to control the applied electric field from both above and below the sample, essentially “tuning,” or selecting, the materials’ quantum state, and thus controlling whether or not the electrons "decide" to respond to a magnetic field by forming a fractional quantum Hall state.
This discovery required the unique combination of high magnetic fields with very low temperatures (down to 20 millikelvin) – a pairing available at the National High Magnetic Field Laboratory. Measurements were performed in the lab’s DC Field Facility at the Florida State University headquarters location using several unique magnet systems spanning fields from 20 to 35 tesla.
“We have established a fantastic relationship with the MagLab over many years,” says Cory Dean, professor of Physics at Columbia University and key researcher in this effort. “The support provided by the NHMFL personnel at both the technical and scientific level has been invaluable to our efforts.”
The Columbia research team is planning to explore these materials at even higher magnetic fields, searching for the existence of theoretically predicted quasi-particles exhibiting properties that lend themselves to applications in quantum computing. Quantum computers, which are still in the early stages of development, use quantum-mechanical phenomena (as opposed to transistors) to perform complex calculations that have proven to be difficult or intractable with existing computers.
“The implications of this research could be far reaching,” Dean added. “The fact that we are able to modify the nature of the fractional quantum Hall effect by electric fields is a really exciting step.”
The National High Magnetic Field Laboratory is the world’s largest and highest-powered magnet facility. Located at Florida State University, the University of Florida and Los Alamos National Laboratory, the interdisciplinary National MagLab hosts scientists from around the world to perform basic research in high magnetic fields, advancing our understanding of materials, energy and life. The lab is funded by the National Science Foundation (DMR-1157490) and the state of Florida. For more information, visit us online at nationalmaglab.org or follow us on Facebook, Twitter, Instagram and Pinterest at NationalMagLab.