wiredinUSA December 2014

More superconductor research

New observations of electron movement in superconductors could accelerate their development. Researcher Zhi-Xun Shen and his team at Stanford University have found that lattice vibrations, known to be damaging to superconductors, can also offer an enhancement. “I’ve been working on superconductors for a long time,” Shen told Chemistry World. “This is a new thing we can try to maybe getmuchbetter superconductors. It doesn’t happen very often, so we’re very excited about it.” Shen’s team studied films using angle resolved photoelectron spectroscopy (ARPES). The scientists used X-rays from the Stanford synchrotron radiation lightsource to eject electrons from iron selenide films, and study their properties including energy

and angular momentum. They found that some electrons had less energy than expected, and that the difference was exactly the energy of the vibrations in the selenium titanate substrate. Shen explained that an individual quantum packet of vibration – a phonon – couples to each electron pair, bringing them together to achieve superconductivity. When the electrons are ejected by X-rays, they lose energy to excite these phonons. “We show unambiguously how the substrate can play a role in enhancing superconductivity,” Shen stated. He added that these phonons should help even when electrons are paired up by phenomena other than lattice ripples. He now plans to attempt to use this approach in other materials, to discover whether sandwiching a superconductor between two substrates could provide greater enhancement.

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