Physicists Demonstrate Coveted 'Spin-Orbit Coupling' in Atomic Gases

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ScienceDaily (Mar. 4, 2011) — Physicists at the Joint Quantum Institute (JQI), a collaboration of the National Institute of Standards and Technology (NIST) and the University of Maryland-College Park, have for the first time caused a gas of atoms to exhibit an important quantum phenomenon known as spin-orbit coupling. Their technique opens new possibilities for studying and better understanding fundamental physics and has potential applications to quantum computing, next-generation "spintronics" devices and even "atomtronic" devices built from ultracold atoms.

In the researchers' demonstration of spin-orbit coupling, two lasers allow an atom's motion to flip it between a pair of energy states. The new work, published in Nature, demonstrates this effect for the first time in bosons, which make up one of the two major classes of particles. The same technique could be applied to fermions, the other major class of particles, according to the researchers. The special properties of fermions would make them ideal for studying new kinds of interactions between two particles -- for example those leading to novel "p-wave" superconductivity, which may enable a long-sought form of quantum computing known as topological quantum computation.

In an unexpected development, the team also discovered that the lasers modified how the atoms interacted with each other and caused atoms in one energy state to separate in space from atoms in the other energy state.

One of the most important phenomena in quantum physics, spin-orbit coupling describes the interplay that can occur between a particle's internal properties and its external properties. In atoms, it usually describes interactions that only occur within an atom: how an electron's orbit around an atom's core (nucleus) affects the orientation of the electron's internal bar-magnet-like "spin." In semiconductor materials such as gallium arsenide, spin-orbit coupling is an interaction between an electron's spin and its linear motion in a material.

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http://www.sciencedaily.com/releases/2011/03/110302131853.htm