Overview of project B04

Non-Equilibrium Dynamics of the Phonon System

Horn-von Hoegen

The excitation and decay of localized vibrations and phonons at the surface of a crystal lattice upon an optical excitation through a femtosecond laser pulse is studied by means of ultrafast electron diffraction with femtosecond temporal resolution. We focus on a fundamental understanding of mechanisms like electron-phonon coupling, which are responsible for the energy transfer from the electron system to the lattice system, phonon-phonon interaction, which causes mode conversion and thermalisation, and direct excitations, which result in an almost immediate stimulation of the lattice.

Ultrathin Pb(111) and Bi(111) films of few layer thickness on Si(111) substrates were used to study energy transfer from the electron system to the lattice system via electron-phonon coupling. While for Bi the bulk is heated up much faster on 3 ps timescale the response of the surface occurs delayed after 12 ps which is attributed to anharmonic coupling of the surface phonon modes to the bulk.

The phonon transport from ultrathin Pb(111) films across the interface into the Si substrate is – even for a thickness of 4 atomic layers – still governed by existing acoustic mismatch (AAM) or diffuse mismatch (DMM) model. Thus, finite size effects in nanoscale heat transport seems to be suppressed even for the thinnest films.




Pablo Maldonado, T. Chase, A. H. Reid, X. Shen, R. K. Li, K. Carva, T. Payer, Michael Horn-von Hoegen, Klaus Sokolowski-Tinten, X. J. Wang, Peter M. Oppeneer and Hermann A. Dürr
Tracking the Ultrafast Nonequilibrium Energy Flow between Electronic and Lattice Degrees of Freedom in Crystalline Nickel
Phys. Rev. B 101, 100302(R) (2020)
DOI: 10.1103/PhysRevB.101.100302

S. Chen, Michael Horn-von Hoegen, Patricia A. Thiel, Adam Kaminski, Benjamin Schrunk, Athanassios Speliotis, E. H. Conrad and Michael C. Tringides
High Layer Uniformity of Two-Dimensional Materials Demonstrated Surprisingly from Broad Features in Surface Electron Diffraction
J. Phys. Chem. Lett. 11, 8937 (2020)
DOI: 10.1021/acs.jpclett.0c02113



Bernd Hafke, Tobias Witte, Christian Brand, Thomas Duden and Michael Horn-von Hoegen
Pulsed Electron Gun for Electron Diffraction at Surfaces with Femtosecond Temporal Resolution and High Coherence Length
Rev. Sci. Instrum. 90, 045119 (2019)
DOI: 10.1063/1.5086124

Verena Tinnemann, Carla Streubühr, Bernd Hafke, Annika Kalus, Anja Hanisch-Blicharski, Manuel Ligges, Dietrich von der Linde, Uwe Bovensiepen and Michael Horn-von Hoegen
Ultrafast Electron Diffraction from a Bi(111) Surface: Impulsive Lattice Excitation and Debye Waller Analysis at Large Momentum Transfer
Struct. Dyn. 6, 035101 (2019)
DOI: 10.1063/1.5093637

Dennis Meyer, Giriraj Jnawali, Hichem Hattab and Michael Horn-von Hoegen
Rapid Onset of Strain Relief by Massive Generation of Misfit Dislocations in Bi(111)/Si(001) Heteroepitaxy
Appl. Phys. Lett. 114, 081601 (2019)
DOI: 10.1063/1.5088760

Karim Omambac, Hichem Hattab, Christian Brand, Giriraj Jnawali, Alpha T. N’Diaye, Johann Coraux, Raoul van Gastel, Bene Poelsema, Thomas Michely, Frank Meyer zu Heringdorf and Michael Horn-von Hoegen
Temperature-Controlled Rotational Epitaxy of Graphene
Nano Lett. 19, 4594 (2019)
DOI: 10.1021/acs.nanolett.9b01565

S. Chen, Michael Horn-von Hoegen, P. A. Thiel and M. C. Tringides
Diffraction Paradox: An Unusually Broad Diffraction Background Marks High Quality Graphene
Phys. Rev. B 100, 155307 (2019)
DOI: 10.1103/PhysRevB.100.155307

Verena Tinnemann, Carla Streubühr, Bernd Hafke, Tobias Witte, Annika Kalus, Anja Hanisch-Blicharski, Manuel Ligges, Ping Zhou, Dietrich von der Linde, Uwe Bovensiepen and Michael Horn-von Hoegen
Decelerated Lattice Excitation and Absence of Bulk Phonon Modes at Surfaces: Ultra-fast Electron Diffraction from Bi(111) Surface upon fs-Laser Excitation
Struct. Dyn. 6, 065101 (2019)
DOI: 10.1063/1.5128275



Tim Frigge, Bernd Hafke, Tobias Witte, Boris Krenzer and Michael Horn-von Hoegen
Non-Equilibrium Lattice Dynamics of One-Dimensional In Chains on Si(111) upon Ultrafast Optical Excitation
Struct. Dyn. 5, 025101 (2018)
DOI: 10.1063/1.5016619



Tobias Witte, Tim Frigge, Bernd Hafke, Boris Krenzer and Michael Horn-von Hoegen
Nanoscale Interfacial Heat Transport of Ultrathin Epitaxial Hetero Films: Few Monolayer Pb(111) on Si(111)
Appl. Phys. Lett. 110, 243103 (2017)
DOI: 10.1063/1.4986509