- LSF ID
- 59817
- ORCID
- 0000-0002-2984-4456
- Sonstiges
- der Hochschule zugeordnete*r Autor*in
- LSF ID
- 55029
- Sonstiges
- der Hochschule zugeordnete*r Autor*in
- LSF ID
- 61635
- ORCID
- 0000-0001-9887-5638
- Sonstiges
- der Hochschule zugeordnete*r Autor*in
- LSF ID
- 62299
- ORCID
- 0000-0002-2903-2933
- Sonstiges
- der Hochschule zugeordnete*r Autor*in
- GND
- 1201039908
- LSF ID
- 10366
- ORCID
- 0000-0003-0324-3457
- Sonstiges
- der Hochschule zugeordnete*r Autor*in
korrespondierende*r Autor*in
Abstract:
Upon impulsive optical excitation of solid-state materials, the non-equilibrium flow of energy from the excited electronic system to the lattice degrees of freedom typically happens in a few picoseconds. Here we identified the surface of thin Bi films grown on Si(001) as an additional subsystem which is excited much slower on a 100 ps timescale that is caused by decoupling due to mismatched phonon dispersions relations of bulk and surface. Anharmonic coupling among the phonon systems provides pathways for excitations which exhibits a 1/T-dependence causing a speed-up of surface excitation at higher temperatures. A quantitative justification is provided by phonon Umklapp processes from lattice thermal conductivity of the Bi bulk. Three-temperature model simulations reveal a pronounced non-equilibrium situation up to nanoseconds: initially, the surface is colder than the bulk, that situation is then inverted during cooling and the surface feeds energy back into the bulk phonon system.