'Accidental' purple bronze find paves way for high temp superconductivity

A team of researchers has found an unusual property of purple bronze, which could lead to high-temperature superconductivity.

While studying purple bronze, a molybdenum oxide, the researchers at the U.S. Department of Energy's (DOE) Ames Laboratory discovered an unconventional charge density wave on its surface.

A charge density wave (CDW) is a state of matter where electrons bunch together in a repeating pattern, like a standing wave on the surface of water.

Superconductivity and charge density waves share a common origin, often co-exist, and can compete for dominance in certain materials.

Conventional CDWs and superconductivity both arise from electron-phonon interactions, the interaction of electrons with the vibrations of the crystal lattice. Electron-electron interactions are the likely origin of unconventional, high-temperature superconductivity such as found in copper- and iron-based compounds.

Unconventional, electron-electron driven CDW are extremely rare and its discovery here is important, because the material showed an 'extraordinary' increase of CDW transition temperature and a huge increase of energy gap at the surface.

Both are properties essential for CDW and high-temperature superconductivity," explained Adam Kaminski, adding "This was an accidental but very exciting discovery. We were studying this material because its one-dimensional structure makes it quite interesting. We saw strange things happening to the electronic band structure, but when we looked at the surface we were stunned by extraordinary enhancement of transition temperature and energy gap."

The study is featured as an Editor's Suggestion in Physical Review Letters.