Picture of the Month - December 2017
Here you see current insights into the research of the LaMa groups. A collection of the former pictures can be found in the Gallery.
Driving surface dynamics at the quantum limit
Do optically driven phase transitions at surfaces occur at different time scales than corresponding bulk transitions? We have investigated the photo-induced melting of the insulating, low temperature phase of In-wires at the Si(111) surface [(8x2) honeycomb chains, left hand side] by fs-laser pulse [1]. A long-lived (440 ps), supercooled metallic phase is created [the high temperature (4x1) uniform chains, right hand side]. Thereby, the system remains well below the critical temperature. Diffraction techniques and DFT-based adiabatic molecular dynamics reveals that the optical excitation breaks and creates In–In bonds, leading to the non-thermal excitation of soft phonon modes. The transition is driven within 350 fs and is thus as fast as those in bulk materials in the non-thermal regime [2].
Publications:
[1] S. Wall et al., «Atomistic picture of charge density wave formation at surfaces»,
Phys. Rev. Lett. 109, 186101 (2012). doi: https://doi.org/10.1103/PhysRevLett.109.186101
[2] T. Frigge et al., «Optically excited structural transition in atomic wires at surfaces at the quantum limit», Nature 544, 207-211 (2017). doi: https://doi.org/10.1038/nature21432
This picture was provided by Prof. Dr. Simone Sanna.
