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May 17, 2007

Polariton Superfluid: Laser version of superconductors in new form of matter

Physicists at the University of Pittsburgh have demonstrated a new form of matter that melds the characteristics of lasers with those of the world's best electrical conductors - superconductors.

This is another example of more than one new state of matter being created every year The most familiar examples of states of matter are solids, liquids, and gases; the most common state of matter in the universe is plasma. Less familiar phases include: quark-gluon plasma; Bose-Einstein condensates and fermionic condensates; strange matter; superfluids and supersolids, and possibly string-net liquids.

The new state (polariton superfluid) is a solid filled with a collection of energy particles known as polaritons that have been trapped and slowed, explained lead investigator David Snoke, an associate professor in the physics and astronomy department in Pitt's School of Arts and Sciences.

Using specially designed optical structures with nanometer-thick layers-which allow polaritons to move freely inside the solid-Snoke and his colleagues captured the polaritons in the form of a superfluid. In superfluids and in their solid counterparts, superconductors, matter consolidates to act as a single energy wave rather than as individual particles.

In superconductors, this allows for the perfect flow of electricity. In the new state of matter demonstrated at Pitt-which can be called a polariton superfluid-the wave behavior leads to a pure light beam similar to that from a laser but is much more energy efficient.

The polariton superfluid is more stable at higher temperatures, and may be capable of being demonstrated at room temperature in the near future.

Snoke's polariton trap was devised with a technique similar to that used for superfluids made of atoms in a gaseous state known as the Bose-Einstein condensate.


Further reading:
Wikipedia discusses polatitons as quasiparticles resulting from strong coupling of electromagnetic waves with an electric or magnetic dipole-carrying excitation.

Wikipedia discusses polaritronics as an intermediate regime between photonics and sub-microwave electronics. In this regime, signals are carried by an admixture of electromagnetic and lattice vibrational waves known as phonon-polaritons, rather than currents or photons.

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