TY  - JOUR
A1  - de Jong, S.
A1  - Kukreja, R.
A1  - Trabant, C.
A1  - Pontius, N.
A1  - Chang, C. F.
A1  - Kachel, T.
A1  - Beye, Martin
A1  - Sorgenfrei, Florian
A1  - Back, C. H.
A1  - Braeuer, B.
A1  - Schlotter, W. F.
A1  - Turner, J. J.
A1  - Krupin, O.
A1  - Doehler, M.
A1  - Zhu, D.
A1  - Hossain, M. A.
A1  - Scherz, A. O.
A1  - Fausti, D.
A1  - Novelli, F.
A1  - Esposito, M.
A1  - Lee, W. S.
A1  - Chuang, Y. D.
A1  - Lu, D. H.
A1  - Moore, R. G.
A1  - Yi, M.
A1  - Trigo, M.
A1  - Kirchmann, P.
A1  - Pathey, L.
A1  - Golden, M. S.
A1  - Buchholz, Marcel
A1  - Metcalf, P.
A1  - Parmigiani, F.
A1  - Wurth, W.
A1  - Föhlisch, Alexander
A1  - Schuessler-Langeheine, Christian
A1  - Duerr, H. A.
T1  - Speed limit of the insulator-metal transition in magnetite
JF  - Nature materials
N2  - As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown(1), magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible(2-8). Recently, three- Fe- site lattice distortions called trimeronswere identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase(9). Here we investigate the Verwey transition with pump- probe X- ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two- step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5 +/- 0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics(10).
Y1  - 2013
U6  - https://doi.org/10.1038/NMAT3718
SN  - 1476-1122
SN  - 1476-4660
VL  - 12
IS  - 10
SP  - 882
EP  - 886
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Dell'Angela, M.
A1  - Anniyev, Toyli
A1  - Beye, Martin
A1  - Coffee, Ryan
A1  - Föhlisch, Alexander
A1  - Gladh, J.
A1  - Katayama, T.
A1  - Kaya, S.
A1  - Krupin, O.
A1  - LaRue, J.
A1  - Mogelhoj, A.
A1  - Nordlund, D.
A1  - Norskov, J. K.
A1  - Oberg, H.
A1  - Ogasawara, H.
A1  - Ostrom, H.
A1  - Pettersson, Lars G. M.
A1  - Schlotter, W. F.
A1  - Sellberg, J. A.
A1  - Sorgenfrei, Florian
A1  - Turner, J. J.
A1  - Wolf, M.
A1  - Wurth, W.
A1  - Nilsson, A.
T1  - Real-time observation of surface bond breaking with an X-ray Laser
JF  - Science
N2  - We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.
Y1  - 2013
U6  - https://doi.org/10.1126/science.1231711
SN  - 0036-8075
VL  - 339
IS  - 6125
SP  - 1302
EP  - 1305
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Katayama, T.
A1  - Anniyev, Toyli
A1  - Beye, Martin
A1  - Coffee, Ryan
A1  - Dell'Angela, M.
A1  - Föhlisch, Alexander
A1  - Gladh, J.
A1  - Kaya, S.
A1  - Krupin, O.
A1  - Nilsson, A.
A1  - Nordlund, D.
A1  - Schlotter, W. F.
A1  - Sellberg, J. A.
A1  - Sorgenfrei, Florian
A1  - Turner, J. J.
A1  - Wurth, W.
A1  - Öström, H.
A1  - Ogasawara, H.
T1  - Ultrafast soft X-ray emission spectroscopy of surface adsorbates using an X-ray free electron laser
JF  - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy
N2  - We report on an experimental system designed to probe chemical reactions on solid surfaces on a sub-picosecond timescale using soft X-ray emission spectroscopy at the Linac Coherent Light Source (LCLS) free electron laser (FEL) at the SLAC National Accelerator Laboratory. We analyzed the O 1s X-ray emission spectra recorded from atomic oxygen adsorbed on a Ru(0001) surface at a synchrotron beamline (SSRL, BL13-2) and an FEL beamline (LCLS, SXR). We have demonstrated conditions that provide negligible amount of FEL induced damage of the sample. In addition we show that the setup is capable of tracking the temporal evolution of electronic structure during a surface reaction of submonolayer quantities of CO molecules desorbing from the surface.
KW  - X-ray emission spectroscopy
KW  - Surface science
KW  - Free electron laser
KW  - Ultrafast
Y1  - 2013
U6  - https://doi.org/10.1016/j.elspec.2013.03.006
SN  - 0368-2048
VL  - 187
IS  - 1
SP  - 9
EP  - 14
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ostrom, H.
A1  - Oberg, H.
A1  - Xin, H.
A1  - Larue, J.
A1  - Beye, Martin
A1  - Gladh, J.
A1  - Ng, M. L.
A1  - Sellberg, J. A.
A1  - Kaya, S.
A1  - Mercurio, G.
A1  - Nordlund, D.
A1  - Hantschmann, Markus
A1  - Hieke, F.
A1  - Kuehn, D.
A1  - Schlotter, W. F.
A1  - Dakovski, G. L.
A1  - Turner, J. J.
A1  - Minitti, M. P.
A1  - Mitra, A.
A1  - Moeller, S. P.
A1  - Föhlisch, Alexander
A1  - Wolf, M.
A1  - Wurth, W.
A1  - Persson, Mats
A1  - Norskov, J. K.
A1  - Abild-Pedersen, Frank
A1  - Ogasawara, Hirohito
A1  - Pettersson, Lars G. M.
A1  - Nilsson, A.
T1  - Probing the transition state region in catalytic CO oxidation on Ru
JF  - Science
N2  - Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the OK-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.
Y1  - 2015
U6  - https://doi.org/10.1126/science.1261747
SN  - 0036-8075
SN  - 1095-9203
VL  - 347
IS  - 6225
SP  - 978
EP  - 982
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Pontius, N.
A1  - Kachel, T.
A1  - Schüssler-Langeheine, C.
A1  - Schlotter, W. F.
A1  - Beye, Martin
A1  - Sorgenfrei, Florian
A1  - Chang, C. F.
A1  - Föhlisch, Alexander
A1  - Wurth, W.
A1  - Metcalf, P.
A1  - Leonov, I.
A1  - Yaresko, A.
A1  - Stojanovic, N.
A1  - Berglund, Martin
A1  - Guerassimova, N.
A1  - Duesterer, S.
A1  - Redlin, H.
A1  - Duerr, H. A.
T1  - Time-resolved resonant soft x-ray diffraction with free-electron lasers  femtosecond dynamics across the Verwey transition in magnetite
JF  - Applied physics letters
N2  - Resonant soft x-ray diffraction (RSXD) with femtosecond (fs) time resolution is a powerful tool for disentangling the interplay between different degrees of freedom in strongly correlated electron materials. It allows addressing the coupling of particular degrees of freedom upon an external selective perturbation, e. g., by an optical or infrared laser pulse. Here, we report a time-resolved RSXD experiment from the prototypical correlated electron material magnetite using soft x-ray pulses from the free-electron laser FLASH in Hamburg. We observe ultrafast melting of the charge-orbital order leading to the formation of a transient phase, which has not been observed in equilibrium.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3584855
SN  - 0003-6951
VL  - 98
IS  - 18
PB  - American Institute of Physics
CY  - Melville
ER  -