Scientists get first direct look at how electrons ‘dance’ with vibrating atoms

Scientists at the SLAC National Accelerator Laboratory and Stanford University - one of the leading authors, Simon Gerber, has in the meantime relocated to PSI - have made the first direct measurements, and by far the most precise ones, of how electrons move in sync with atomic vibrations rippling through an quantum material, in the present study an unconventional superconductor, as if they were “dancing" to the same beat.

The atomic vibrations are called phonons and the measured electron-phonon coupling, for certain electron “orbitals", was 10 times stronger than standard theory had predicted – making it strong enough to potentially play a role in unconventional superconductivity, which allows materials to conduct electricity with no loss at unexpectedly high temperatures.

The approach developed enables a direct and highly precise way to study a wide range of “emergent” materials whose surprising properties arise from the collective behaviour of fundamental particles, such as electrons. The new approach investigates these materials through high-precision experiments alone, rather than relying on assumptions based on theory.

The experiments were carried out with SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser, combined with time- and angle-resolved photoemission spectroscopy (trARPES) on the Stanford campus. A thick, atomically uniform iron selenide film was hit with infrared laser light to excite its 5 terahertz atomic vibrations. The team then measured the material’s phonon and electron behaviour in two separate experiments. One of the studies leading authors, Simon Gerber, earlier a postdoctoral researcher in Prof. Zhi-Xun Shen’s group at SLAC and Stanford University, led the LCLS measurements; he has since joined the SwissFEL team at PSI as a staff scientist. The researchers described the study today in Science. (Text based on SLAC press release) / Press release PSI