Princeton researchers performed an experiment revealing unlikely behavior in a class of materials called frustrated magnets. In so doing, they addressed a long-debated question about the nature of these discontented quantum materials.

Researchers analyzed the frustrated magnets to see if they exhibit a behavior called the Hall Effect.

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When a magnetic field is applied an electricity flowing in a conductor such as a copper ribbon, the current deflects to a single side of the ribbon. This deflection, first observed in 1879 by E.H. Hall, is utilized in sensors in computer printers and automobile anti-lock braking systems.

The Hall Effect occurs in charge-carrying particles. Most physicists thought it would be impossible to see such behavior in non-charged, or neutral particles like those in frustrated magnets.

Nonetheless, some theorists speculated the neutral particles in frustrated magnets could possibly bend to the Hall rule at extremely cold conditions, close to absolute zero, where particles behave according to the laws of quantum mechanics rather than the classical physical laws. Harnessing quantum behavior could enable game-altering innovations in computing and electronic devices.

The team composed of N. Phuan Ong, Princeton's Eugene Higgins Professor of Physics, and colleague Robert Cava, Princeton's Russell Wellman Moore Professor of Chemistry, and their graduate students Max Hirschberger and Jason Krizan turned to a class of the magnets called pyrochlores.

Pyrochlores contain magnetic moments that at very low temperatures near absolute zero should line-up in an orderly manner so all of their "spins," a quantum-mechanical property, point in the same direction.

Instead, the experiments found the spins point in random directions. These frustrated materials are also referred to as "quantum spin ice."

"These materials are very interesting because theorists think the tendency for spins to align is still there, but due to a concept called geometric frustration, the spins are entangled but not ordered," Ong said.

Entanglement is a key property of quantum systems that researchers hope to harness for building a quantum computer, which could solve problems that today's computers can't handle.

Cava said the use of experiments to probe the quantum behavior of materials is essential for broadening our understanding of fundamental physical properties and the eventual exploitation of this understanding in new technologies.

TagsPhysicicts Decipher "Frustrated Magnets" Using Hall Effect, frustrated magnets, Hall Effect, physics, quantum physics, particles