Understanding tiny reactions: Cold atoms and nanotubes come together in atomic 'black hole'

April 6, 2010 By Steve Bradt, Harvard University
Launched laser-cooled atoms are captured by a single, suspended, single-wall carbon nanotube charged to hundreds of volts. A captured atom spirals towards the nanotube (white path) and reaches the environs of the tube surface, where its valence electron (yellow) tunnels into the tube. The resulting ion (purple) is ejected and detected, and the dynamics at the nanoscale are sensitively probed. Credit: Anne Goodsell and Tommi Hakala/Harvard University

(PhysOrg.com) -- Carbon nanotubes, long touted for applications in materials and electronics, may also be the stuff of atomic-scale black holes.

Physicists at Harvard University have found that a high-voltage nanotube can cause to spiral inward under dramatic acceleration before disintegrating violently. Their experiments, the first to demonstrate something akin to a black hole at atomic scale, are described in the current issue of the journal .

"On a scale of , we create an inexorable and destructive pull similar to what exert on matter at cosmic scales," says Lene Vestergaard Hau, Mallinckrodt Professor of Physics and of Applied Physics at Harvard. "As importantly for scientists, this is the first merging of cold-atom and nanoscale science, and it opens the door to a new generation of cold atom experiments and nanoscale devices."

Hau and co-authors Anne Goodsell, Trygve Ristroph, and Jene A. Golovchenko laser-cooled clouds of one million atoms to just a fraction of a degree above . The physicists then launched this millimeter-long atomic cloud towards a suspended carbon nanotube, located some two centimeters away and charged to hundreds of volts.

The vast majority of the atoms passed right by the wire, but those that came within a micron of it -- roughly 10 atoms in every million-atom cloud -- were inescapably attracted, reaching high speeds as they spiraled toward the nanotube.

"From a start at about 5 meters per second, the cold atoms reach speeds of roughly 1,200 meters per second, or more than 2,700 miles per hour, as they circle the nanotube," says Goodsell, a graduate student on the project and now a postdoctoral researcher in physics at Harvard. "As part of this tremendous acceleration, the temperature corresponding to the atoms' kinetic energy increases from 0.1 degrees Kelvin to thousands of degrees Kelvin in less than a microsecond."

At this point, the speeding separate into an electron and an ion rotating in parallel around the nanowire, completing each orbit in just a few trillionths of a second. The electron eventually gets sucked into the nanotube via quantum tunneling, causing its companion ion to shoot away -- repelled by the strong charge of the 300-volt nanotube -- at a speed of roughly 26 kilometers per second, or 59,000 miles per hour.

The entire experiment was conducted with great precision, allowing the scientists unprecedented access to both cold-atom and nanoscale processes.

"Cold-atom and nanoscale science have each provided exciting new systems for study and applications," says Golovchenko, Rumford Professor of Physics and Gordon McKay Professor of Applied Physics at Harvard. "This is the first experimental realization of a combined cold atom-nanostructure system. Our system demonstrates sensitive probing of atom, electron, and ion dynamics at the nanoscale."

The single-walled carbon nanotube used in these researchers' successful experiment was dubbed "Lucy," and its contributions are acknowledged in the Physical Review Letters paper. The nanotube was grown by chemical vapor deposition across a 10-micron gap in a silicon chip that provides the nanowire with both mechanical support and electrical contact.

"From the atom's point of view, the nanotube is infinitely long and thin, creating a singular effect on the atom," Hau says.

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2.2 / 5 (10) Apr 06, 2010
this reminds me of that article posted a day or so ago regarding particles behaving as though they are all micro-blackholes. I believe this to be proof that this is the case, proof without having to go to the LHC to demonstrate that this concept is a more appropriate rationale for modeling physics.
1.8 / 5 (6) Apr 06, 2010
I believe this supports the theory that the unbalance between matter and antimatter was caused by the abrupt acceleration of the Universe after the Big Bang, causing some antimatter to be destroyed but allowing the counterparts to escape as the Universe expanded.
3.3 / 5 (17) Apr 06, 2010
I'm normally not into weapons and such, but the first thing that came to my mind while reading this article was:

"Mass driver"

And at 26km/s a rather scarry one.. Just needs a carefuly designed injection stage.
2.3 / 5 (3) Apr 07, 2010
Very interesting, and a scaled up version may have practical applications...

Let's take a nanotube and connect it to a van de Graff generator. If the potential on the nanotube is above one MeV, you should see electron and positron pair production from the vaccuum. The electric field would provide enough energy to separate the two virtual particles.

The interesting case is where the positrons are repelled from the nanotube. A highly efficient source of cold positrons.
not rated yet Apr 07, 2010
"Mass driver"

I was more thinking along the lines of 'propulsuion system for spacecraft'

Though at 10 ppm efficiency it's not very good - but the particles that are not accelerated could be caught and re-used.
not rated yet Apr 08, 2010
Perhaps a grid of Nanotubes cold capture more and be a better power producer but this is a promising start at least
5 / 5 (1) Apr 10, 2010
It would appear that there will be any number of applications derived from this experimental result, but I have to object to a phenomenon essentially electrical in nature being linked to the notion of it somehow being a "Black Hole".

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