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Dezember

Bild des Monats Dezember 2017

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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

Dieses Bild wurde eingereicht von Prof. Dr. Simone Sanna.