Dynamical screening effects in pump-probe Hard X-ray Photoelectron Spectroscopy

2016 Fiscal Year Annual Research Report

• Project/Area Number: 15K13526
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Chainani Ashish 国立研究開発法人理化学研究所, 放射光科学総合研究センター, 専任研究員 (80425636)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: Time-resolved / pump-probe / HAXPES

Outline of Annual Research Achievements

We have carried out Time-resolved hard X-ray photoelectron spectroscopy (trHAXPES) using microfocused X-ray free-electron laser (XFEL, hn =8 keV) pulses as a probe and infrared laser pulses (hn = 1:55 eV) as a pump to determine space-charge effects and separate out intrinsic charge-carrier recombination dynamics in La:SrTiO3. We have used a combination of experiments and numerical N-body simulations for developing a simple approach to characterize and decrease XFEL-induced vacuum space-charge effects, which otherwise pose a serious limitation to spectroscopy experiments. We then show that, using an analytical mean-field model, vacuum space-charge effects can be compensated by pump laser-induced photoholes at high excitation densities. This provides us a method to separate vacuum space-charge effects from the intrinsic charge-carrier recombination dynamics in the time domain. We then obtain pump laser induced charge carrier dynamics form the Ti 1s peak width and peak energy shift as function of time delay between the pump and the probe using trHAXPES. Our trHAXPES results thus open a route to studies of intrinsic charge-carrier dynamics on picosecond time scales with lateral spatial resolution on the micrometer scale.

Research Products

• [Journal Article] Hard x-ray photoelectron spectroscopy experiment at SACLA ~ towards femtosecond time-resolved measurement (2016)
  • Author(s): M. Oura, L.-P. Oloff. K Rossnagel, A. Chainani and M. Matsunami
  • Journal Title: Journal of Japanese Society for Synchrotron Radiation Research Volume: 29 Pages: 14 to 22
  • Peer Reviewed
• [Journal Article] Time-resolved HAXPES using a microfocused XFEL beam: From vacuum space-charge effects to intrinsic charge-carrier recombination dynamics (2016)
  • Author(s): L.-P. Oloff, A. Chainani, M. Matsunami, K. Takahashi, T. Togashi, H. Osawa, K. Hanff, A. Quer, R. Matsushita, R. Shiraishi, M. Nagashima, A. Kimura, K. Matsuishi, M. Yabashi, Y. Tanaka, G. Rossi, T. Ishikawa, K. Rossnagel and M. Oura
  • Journal Title: Scientific Reports Volume: 6 Pages: 35087-1 to 10
  • DOI: doi:10.1038/srep35087 (2016)
  • Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
• [Book] Springer Series in Surface Sciences, Hard X-ray Photoelectron Spectroscopy (HAXPES) (2016)
  • Author(s): L.-P. Oloff, M. Oura, A. Chainani and K Rossnagel
  • Total Pages: 555 to 568
  • Publisher: Springer International