Twisted Physics

Professor Allan MacDonald wondered what would happen if you stacked two atom-thin sheets of a material called graphene on top of each other, but with a slight twist so the atoms in one sheet didn’t perfectly line up with atoms on the other. Using supercomputers at the Texas Advanced Computing Center, he and another researcher modeled the problem of twisted bilayer graphene and found that at a very specific angle electrons in the model behaved in a strange and extraordinary way.

MacDonald, who holds the Sid W. Richardson Foundation Regents Chair in Physics, was surprised to see the atoms suddenly moved more than 100 times more slowly at the 1.1 degree angle. Discovering this “magic angle” effectively launched a new subfield called twistronics.

For decades, scientists have worked to find a material that can transport electricity with perfect efficiency — or superconduct — at something like room temperature. (Current superconductors require closer to absolute-zero temperatures.) Such a discovery would have implications for quantum computing and for efficient sources of electricity. In 2018, scientists demonstrated that bilayer graphene twisted at MacDonald’s magic angle exhibits superconductivity — and at a surprisingly high temperature, too.

In 2020, MacDonald won the Wolf Prize, one of the most prestigious prizes in physics. He continues to make discoveries about magic-angle graphene, including with research findings that suggest great promise for future advances in electronics and improvements in energy.

“The thing that’s energized my work is that nature is always posing new problems,” MacDonald said. “When you ask a new type of question, you don’t know in advance what the answer is or where the adventure will lead.”