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Friday, 26 June, 2009

It runs and runs and runs ...

NIM physicists invent the smallest electric motor world-wide

The principle is easy: one starter and one motor atom in a ring of laser light - and a bit of fine tuning, in order to keep moving into the right direction.

The research group around the theoretical physicist Prof. Peter Hänggi from the University of Augsburg has invented a concept for the minimal version of an electric motor, which runs on merely two atoms. The study has recently been published in the renowned scientific journal Physical Review Letters.
An ordinary electric motor is based on the principle that mechanical work is done by electrical energy. Hänggi and his co-authors Dr. Alexey Ponomarev and Dr. Sergey Denisov have now transferred this principle into the nano world, even to the level of single atoms. „Since on this level not the laws of classical phy­sics, but those of quantum mechanics are applicable, the conversion of electric energy into mechanical work is not a trivial challenge,” Hänggi stresses. The three physicists have now met this challenge.
They designed a magnetically dri­ven atomic quantum motor by first “catching” two atoms in a ring of laser light - one motor and one starter atom. This construction becomes a motor when mo­tor and starter atom meet, then interact via electro-magnetic forces, which results in the starter atom giving the motor atom a “kick”.
“Since there is no friction in this world, it is crucial to determine a moving direction for the motor once it has been kicked off, in order to enable it to perform work against an outer force”, explains Hänggi. To keep the motor atom on its course, specifically tuned external electro-dynamic forces are required. “This ‘tuning’, which avoids a false turn-over of the motor atom in the ring, is the crux”, emphasizes Hänggi. He even has a technical term for it: "breaking of symmetry”.
Speaking of tuning: What makes this smallest motor of the world superior to other motors: “After switching off the electro-magnetic drive, it simply keeps on running, because there is no bra­king friction in its quantum world, con­sisting of only two atoms.”

Publication:
„ac-Driven Atomic Quantum Mo­tor“, A. V. Ponomarev, S. Denisov, and P. Hänggi. , Phys. Rev. Lett. 102, 230601 (2009)

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