TY  - JOUR
A1  - Sander, Mathias
A1  - Pudell, Jan-Etienne
A1  - Herzog, Marc
A1  - Bargheer, Matias
A1  - Bauer, R.
A1  - Besse, V.
A1  - Temnov, V.
A1  - Gaal, P.
T1  - Quantitative disentanglement of coherent and incoherent laser-induced surface deformations by time-resolved x-ray reflectivity
JF  - Applied physics letters
N2  - We present time-resolved x-ray reflectivity measurements on laser excited coherent and incoherent surface deformations of thin metallic films. Based on a kinematical diffraction model, we derive the surface amplitude from the diffracted x-ray intensity and resolve transient surface excursions with sub-angstrom spatial precision and 70 ps temporal resolution. The analysis allows for decomposition of the surface amplitude into multiple coherent acoustic modes and a substantial contribution from incoherent phonons which constitute the sample heating. Published by AIP Publishing.
Y1  - 2017
U6  - https://doi.org/10.1063/1.5004522
SN  - 0003-6951
SN  - 1077-3118
VL  - 111
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Sander, Mathias
A1  - Herzog, Marc
A1  - Pudell, Jan-Etienne
A1  - Bargheer, Matias
A1  - Weinkauf, N.
A1  - Pedersen, M.
A1  - Newby, G.
A1  - Sellmann, J.
A1  - Schwarzkopf, J.
A1  - Besse, V.
A1  - Temnov, V. V.
A1  - Gaal, P.
T1  - Spatiotemporal Coherent Control of Thermal Excitations in Solids
JF  - Physical review letters
N2  - X-ray reflectivity measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatiotemporal coherent control of thermally induced surface deformations on ultrafast time scales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-angstrom resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period. can be canceled by a second, time-delayed TG excitation shifted by Lambda/2. The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevLett.119.075901
SN  - 0031-9007
SN  - 1079-7114
VL  - 119
SP  - 102
EP  - 110
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Mor, Selene
A1  - Herzog, Marc
A1  - Golez, Denis
A1  - Werner, Philipp
A1  - Eckstein, Martin
A1  - Katayama, Naoyuki
A1  - Nohara, Minoru
A1  - Takagi, Hide
A1  - Mizokawa, Takashi
A1  - Monney, Claude
A1  - Staehler, Julia
T1  - Ultrafast Electronic Band Gap Control in an Excitonic Insulator
JF  - Physical review letters
N2  - We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta2NiSe5 investigated by time-and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of F-C = 0.2 mJ cm(-2), the band gap narrows transiently, while it is enhanced above FC. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of Ta2NiSe5, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta2NiSe5 with light on the femtosecond time scale.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevLett.119.086401
SN  - 0031-9007
SN  - 1079-7114
VL  - 119
SP  - 11559
EP  - 11567
PB  - American Physical Society
CY  - College Park
ER  -