-
The Heisenberg-RIXS instrument at the European XFEL
Authors:
Justine Schlappa,
Giacomo Ghiringhelli,
Benjamin E. Van Kuiken,
Martin Teichmann,
Piter S. Miedema,
Jan Torben Delitz,
Natalia Gerasimova,
Serguei Molodtsov,
Luigi Adriano,
Bernard Baranasic,
Carsten Broers,
Robert Carley,
Patrick Gessler,
Nahid Ghodrati,
David Hickin,
Le Phuong Hoang,
Manuel Izquierdo,
Laurent Mercadier,
Giuseppe Mercurio,
Sergii Parchenko,
Marijan Stupar,
Zhong Yin,
Leonardo Martinelli,
Giacomo Merzoni,
Ying Ying Peng
, et al. (22 additional authors not shown)
Abstract:
Resonant Inelastic X-ray Scattering (RIXS) is an ideal X-ray spectroscopy method to push the combination of energy and time resolutions to the Fourier transform ultimate limit, because it is unaffected by the core-hole lifetime energy broadening. And in pump-probe experiments the interaction time is made very short by the same core-hole lifetime. RIXS is very photon hungry so it takes great advant…
▽ More
Resonant Inelastic X-ray Scattering (RIXS) is an ideal X-ray spectroscopy method to push the combination of energy and time resolutions to the Fourier transform ultimate limit, because it is unaffected by the core-hole lifetime energy broadening. And in pump-probe experiments the interaction time is made very short by the same core-hole lifetime. RIXS is very photon hungry so it takes great advantage from high repetition rate pulsed X-ray sources like the European XFEL. The hRIXS instrument is designed for RIXS experiments in the soft X-ray range with energy resolution approaching the Fourier and the Heisenberg limits. It is based on a spherical grating with variable line spacing (VLS) and a position-sensitive 2D detector. Initially, two gratings are installed to adequately cover the whole photon energy range. With optimized spot size on the sample and small pixel detector the energy resolution can be better than 40 meV at any photon energy below 1000 eV. At the SCS instrument of the European XFEL the spectrometer can be easily positioned thanks to air-pads on a high-quality floor, allowing the scattering angle to be continuously adjusted over the 65-145 deg range. It can be coupled to two different sample interaction chamber, one for liquid jets and one for solids, each equipped at the state-of-the-art and compatible for optical laser pumping in collinear geometry. The measured performances, in terms of energy resolution and count rate on the detector, closely match design expectations. hRIXS is open to public users since the summer of 2022.
△ Less
Submitted 13 March, 2024;
originally announced March 2024.
-
Ultrafast modulation of the chemical potential in BaFe$_2$As$_2$ by coherent phonons
Authors:
L. X. Yang,
G. Rohde,
T. Rohwer,
A. Stange,
K. Hanff,
C. Sohrt,
L. Rettig,
R. Cortés,
F. Chen,
D. L. Feng,
T. Wolf,
B. Kamble,
I. Eremin,
T. Popmintchev,
M. M. Murnane,
H. C. Kapteyn,
L. Kipp,
J. Fink,
M. Bauer,
U. Bovensiepen,
K. Rossnagel
Abstract:
Time- and angle-resolved extreme ultraviolet photoemission spectroscopy is used to study the electronic structure dynamics in BaFe$_2$As$_2$ around the high-symmetry points $Γ$ and $M$. A global oscillation of the Fermi level at the frequency of the $A_{1g}$(As) phonon mode is observed. It is argued that this behavior reflects a modulation of the effective chemical potential in the photoexcited su…
▽ More
Time- and angle-resolved extreme ultraviolet photoemission spectroscopy is used to study the electronic structure dynamics in BaFe$_2$As$_2$ around the high-symmetry points $Γ$ and $M$. A global oscillation of the Fermi level at the frequency of the $A_{1g}$(As) phonon mode is observed. It is argued that this behavior reflects a modulation of the effective chemical potential in the photoexcited surface region that arises from the high sensitivity of the band structure near the Fermi level to the $A_{1g}$ phonon mode combined with a low electron diffusivity perpendicular to the layers. The results establish a novel way to tune the electronic properties of iron pnictides: coherent control of the effective chemical potential. The results further suggest that the equilibration time for the effective chemical potential needs to be considered in the ultrafast electronic structure dynamics of materials with weak interlayer coupling.
△ Less
Submitted 20 December, 2013;
originally announced December 2013.
-
Ultrafast melting of a charge-density wave in the Mott insulator 1T-TaS2
Authors:
S. Hellmann,
M. Beye,
C. Sohrt,
T. Rohwer,
F. Sorgenfrei,
H. Redlin,
M. Kalläne,
M. Marczynski-Bühlow,
F. Hennies,
M. Bauer,
A. Föhlisch,
L. Kipp,
W. Wurth,
K. Rossnagel
Abstract:
Femtosecond time-resolved core-level photoemission spectroscopy with a free-electron laser is used to measure the atomic-site specific charge-order dynamics in the charge-density-wave/Mott insulator 1T-TaS2. After strong photoexcitation, a prompt loss of charge order and subsequent fast equilibration dynamics of the electron-lattice system are observed. On the time scale of electron-phonon thermal…
▽ More
Femtosecond time-resolved core-level photoemission spectroscopy with a free-electron laser is used to measure the atomic-site specific charge-order dynamics in the charge-density-wave/Mott insulator 1T-TaS2. After strong photoexcitation, a prompt loss of charge order and subsequent fast equilibration dynamics of the electron-lattice system are observed. On the time scale of electron-phonon thermalization, about 1 ps, the system is driven across a phase transition from a long-range charge ordered state to a quasi-equilibrium state with domain-like short-range charge and lattice order. The experiment opens the way to study the nonequilibrium dynamics of condensed matter systems with full elemental, chemical, and atomic site selectivity.
△ Less
Submitted 4 August, 2010; v1 submitted 27 April, 2010;
originally announced April 2010.