'Third state of magnetism' could advance storage, superconducting

A multidisciplinary team at the Massachusetts Institute of Technology claims to have demonstrated the existence of a long-theorized state of magnetism, called quantum spin liquid (QSL), that could have eventual application in computer memory storage and high-temperature superconductors. QSL is a solid crystal, but the fluctuating magnetic orientations of its individual particles resemble the constant motion of molecules within a liquid.

“We’re showing that there is a third fundamental state for magnetism” in addition to ferromagnetism and anti-ferromagnetism, says MIT physics professor Young Lee, senior author of a paper on the work that appeared in the Dec 20, 2012, issue of Nature (Fractionalized excitations in the spin-liquid state of a kagome-lattice antiferromagnet). There is no static order to the magnetic moments (orientations) within the material, “but there is a strong interaction between them, and due to quantum effects they don’t lock in place,” Lee adds.

The existence of QSLs has been theorized since 1987 but has been difficult to prove. MIT researchers spent 10 months growing a pure crystal of a suspected QSL material, herbertsmithite, and used a neutron spectrometer at the National Institute of Standards and Technology in Gaithersburg, MD, to analyze the material’s structure through neutron scattering.

In their experiments on the crystal, the team found a state with fractionalized excitations; those excited states, called spinons, formed a continuum. “That’s a fundamental theoretical prediction for spin liquids that we are seeing in a clear and detailed way for the first time” through the team’s fundamental research, says Lee.

Practical results are a long ways off, but the work could lead to advances in data storage or communications, perhaps using long-range quantum entanglement.