PORTLAND, Ore. — Superconductors transport electrons with zero resistance by synchronizing their movement through changes in the internal structure of materials. Hence, no physical collisions occur.

The exact character of these changes has been the subject of much speculation, prompting over 100,000 scholarly papers on the subject in the last 20 years. A novel theory developed by university reseachers in the U.S. and China now attempts to explain high-temperature superconductivity using a new class of materials discovered last year called iron pnictides (pronounced NIK-tides).

Researchers will attempt to explain high-temperature superconductivity through a theory of quantum phase changes this week during the American Physical Society (March 16-20) in Pittsburgh. The new approach adds to several competing theories that aim to explain high-temperature superconductivity.

The newest high-temperture superconducting material is a metal called iron pnictides with alternating layers of iron and arsenic

The key to high-temperature superconductors, according to the new theory, is their different "quantum phases," which are similar to the difference between solids and liquids, according to researchers from Rice University, Rutgers University, Zhejiang University and the Los Alamos National Laboratory.

Ice and water are two phases of H²O; above the critical melting point the molecules are ordered as solids, but below it they melt in a disordered liquid. Likewise, above its critical melting point, the quantum phase of high-temperature superconductors is antiferromagnetic; below it, they melt into magnetic disorder.

"Our theory addresses the nature of quantum magnetic fluctuations in the framework of quantum criticality, which has potential relevance to a broad range of materials," said professor Qimiao Si, a physicist from Rice University. He performed the work with researchers Jianhui Dai of Zhejiang University (Hangzhou, China) and Jian-Xin Zhu of Los Alamos National Laboratory.

Quantum criticality defines the transition between phases, possibly explaining superconductivity in iron pnictides, which interleave iron and arsenic in a layered structure similar to cuprates.