Beaten to action

Phys. Rev. Lett. 108, 136801 (2012)

Credit: © 2012 APS

Oxide materials have attracted considerable interest because of their electronic properties such as magnetism, superconductivity and ferroelectricity. However, although factors such as strain have been used successfully to control many of these properties, dynamic aspects such as the role of lattice vibrations remain much less explored. To this end, Andrea Caviglia and colleagues studied thin films of NdNiO₃ grown on a LaAlO₃ substrate, and found that at room temperature NdNiO₃ is metallic and at cryogenic temperatures it is insulating. They then excited the thin films with ultrashort mid-infrared light pulses with energies tuned to typical values for vibrational excitations. For a period of a nanosecond this turns the low-temperature insulating phase metallic. Of course, such metal–insulator transitions have previously been induced by various means, even in this compound. What is so unusual about these results, however, is that the effect occurs when the pump energy corresponds to the lattice vibrations of the substrate, and not of the NdNiO₃ film. These substrate lattice vibrations reach into the film and cause the metal–insulator transition, emphasizing the intricate link between structure and lattice dynamics even across oxide thin-films.