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

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K13526
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• 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 Final Research Achievements

We have carried out Time-resolved hard X-ray photoelectron spectroscopy (trHAXPES) using microfocused X-ray free-electron laser (XFEL, hnu =8 keV) pulses as a probe and infrared laser pulses (hnu = 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. 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. 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.

Free Research Field

Condensed Matter Physics