Physicists report promising approach to harnessing exotic electronic behavior
https://phys.org/news/2021-10-physicist ... ronic.html
by Elizabeth A. Thomson, Materials Research Laboratory, Massachusetts Institute of Technology
For some 50 years scientists have worked to harness Bloch oscillations, an exotic kind of behavior by electrons that could introduce a new field of physics—and important new technologies—much like more conventional electronic behavior has led to everything from smart watches to computers powerful enough to get us to the Moon.
Now, MIT physicists report on a new approach to achieving Bloch oscillations in recently introduced graphene superlattices. Graphene, a material composed of a single layer of carbon atoms arranged in hexagons resembling a honeycomb structure, is an excellent conductor of electricity. Its electronic properties undergo an interesting transformation in the presence of an "electric mesh" (a periodic potential), resulting in new types of electron behavior not seen in pristine materials. In a recent issue of Physical Review Letters, the scientists outline why graphene superlattices may be game changers in the pursuit of Bloch oscillations.
Normally, electrons exposed to a constant electric field accelerate in a straight line. However, quantum mechanics predicts that electrons in a crystal, or material composed of atoms arranged in an orderly fashion, can behave differently. Upon exposure to an electric field, they can oscillate in tiny waves—Bloch oscillations. "This surprising behavior is an iconic example of coherent dynamics in quantum many-body systems," says Leonid Levitov, an MIT professor of physics and leader of the current work. Levitov is also affiliated with MIT's Materials Research Laboratory.
Additional authors are Ali Fahimniya and Zhiyu Dong, both MIT graduate students in physics, and Egor I. Kiselev of Karlsruher Institut fur Technologie.