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New state of matter may lead to novel computer
memory and logic Esoteric property of topological
insulators leads to efficient switching
Physicists have been abuzz over a new state of
matter a topological insulator. These
materials are insulators in their interior, but
their surfaces conduct electricity in an unusual
way the direction of an electrons spin is
always perpendicular to the direction of the
electrons motion as sketched at right. But is
this esoteric property useful for
anything? Researchers at Cornell University
working with colleagues from Penn State, Israel,
and Saudi Arabia have discovered the first
important application of topological insulators.
When a thin magnet is placed on a topological
insulator, current flowing within the topological
insulator can be used to apply a torque to the
magnet, allowing its magnetization direction to
be reoriented. The strength of this effect
(torque per unit current) is at least a factor of
10 greater than any other mechanism for
electrically controlling magnets at room
temperature. This result is exciting in that it
provides a new strategy for the development of
magnetic memory and logic that is much more
energy-efficient and compact than existing
technologies.

In a topological insulator, the spin of an
electron, represented by the red arrows, is
locked perpendicular to its motion (represented
by the green arrows).
A. R. Mellnik, et al. Nature (July 24, 2014).