Graphene under strain produces massive pseudo-magnetic fields

Friday, July 30, 2010

WASHINGTON - Putting the right kind of strain onto a patch of graphene leads to the creation of pseudo-magnetic fields far stronger than the strongest magnetic fields ever sustained in a laboratory, scientists have revealed.

The research, by a multi-institutional team of researchers headed by Michael Crommie, a faculty senior scientist in the Materials Sciences Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley, appears in the journal Science.

“We have shown experimentally that when graphene is stretched to form nanobubbles on a platinum substrate, electrons behave as if they were subject to magnetic fields in excess of 300 tesla, even though no magnetic field has actually been applied. This is a completely new physical effect that has no counterpart in any other condensed matter system,” said Crommie.

Crommie notes that “for over 100 years people have been sticking materials into magnetic fields to see how the electrons behave, but it’s impossible to sustain tremendously strong magnetic fields in a laboratory setting.”

The current record is 85 tesla for a field that lasts only thousandths of a second. When stronger fields are created, the magnets blow themselves apart.

The ability to make electrons behave as if they were in magnetic fields of 300 tesla or more - just by stretching graphene - offers a new window on a source of important applications and fundamental scientific discoveries going back over a century. This is made possible by graphene’s electronic behaviour, which is unlike any other material’s.

“Getting the right strain resulted from a combination of factors. To grow graphene on the platinum we had exposed the platinum to ethylene” - a simple compound of carbon and hydrogen - “and at high temperature the carbon atoms formed a sheet of graphene whose orientation was determined by the platinum’s lattice structure,” Crommie said.

“Controlling where electrons live and how they move is an essential feature of all electronic devices.

New types of control allow us to create new devices, and so our demonstration of strain engineering in graphene provides an entirely new way for mechanically controlling electronic structure in graphene. The effect is so strong that we could do it at room temperature,” he added. (ANI)

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