Are more energy-efficient transistors a step closer?
The discovery paves the way for new types of energy-efficient transistors and circuits.
Conventially speaking when electrons move through a conductive material in an electric field they tend to follow the path of least resistance – which runs in the direction of that field.
The scientists have now found an unexpectedly different behavior under specialized conditions which happens even without the influence of a magnetic field – the only other known way of inducing such a sideways flow.
Two separate streams of electrons would flow in opposite directions, both crosswise to the field, canceling out each other’s electrical charge to produce a “neutral, chargeless current,” explained Leonid Levitov, an MIT professor of physics and a senior author of a paper describing these findings this week in the journal Science.
The exact angle of this current relative to the electric field can be precisely controlled, Levitov said who compares it to a sailboat sailing perpendicular to the wind, its angle of motion controlled by adjusting the position of the sail.
Levitov and co-author Andre Geim aat the University of Manchester suggest the flow could be altered by applying a minute voltage on the gate, allowing the material to function as a transistor. Currents in these materials, being neutral, might not waste much of their energy as heat, as occurs in conventional semiconductors – potentially making the new materials a more efficient basis for computer chips.
“It is widely believed that new, unconventional approaches to information processing are key for the future of hardware,” explained Levitov. “This belief has been the driving force behind a number of important recent developments, in particular spintronics.”
The MIT and University of Manchester researchers have demonstrated a simple transistor based on the new material claims Levitov.
“It is quite a fascinating effect, and it hits a very soft spot in our understanding of complex, so-called topological materials,” suggested G. “It is very rare to come across a phenomenon that bridges materials science, particle physics, relativity, and topology.”
In their experiments, Levitov, Geim, and their colleagues overlaid the graphene on a layer of boron nitride – a two-dimensional material that forms a hexagonal lattice structure, as graphene does. Together, the two materials form a superlattice that behaves as a semiconductor.
The superlattice causes electrons to acquire an unexpected twist – which Levitov describes as “a built-in vorticity” – that changes their direction of motion, much as the spin of a ball can curve its trajectory.
Electrons in graphene behave like massless relativistic particles. The observed effect, however, has no known analog in particle physics, and extends our understanding of how the universe works, the researchers say.
Whether or not this effect can be harnessed to reduce the energy used by computer chips remains an open question, conceded Levitov. This is an early finding, and while there is clearly an opportunity to reduce energy loss to heat locally, other parts of such a system may counterbalance those gains. “This is a fascinating question that remains to be resolved,” said Levitov.
Related articles and links:
www.mit.edu
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