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Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
Published on: October 9, 2012
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Tracking Primary Thermalization Events in Graphene with Photoemission at Extreme Time Scales
I Gierz1, F Calegari1,2, S Aeschlimann1
1Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany.
Physical Review Letters
|September 5, 2015
Summary
Inverse Auger scattering dominates early hot carrier relaxation in graphene, as shown by ultrafast extreme-ultraviolet spectroscopy. This finding guides future petahertz electronics by revealing ultrafast carrier dynamics.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Ultrafast Spectroscopy
Background:
- Direct and inverse Auger scattering are key mechanisms for hot carrier thermalization in semiconductors.
- Inverse Auger scattering is typically suppressed due to energy requirements, but is predicted to dominate in gapless materials like graphene.
Purpose of the Study:
- To experimentally investigate the role of inverse Auger scattering in graphene at early time delays.
- To track the dynamics of excited electrons and their kinetic energy following photoexcitation.
Main Methods:
- Utilized <8 fs extreme-ultraviolet pulses for excitation.
- Employed time-and angle-resolved photoemission spectroscopy to monitor carrier behavior.
- Analyzed changes in conduction band carrier density and average kinetic energy.
Main Results:
- Observed an increase in conduction band carrier density within 25 fs after pump pulse absorption.
- Detected a simultaneous decrease in average carrier kinetic energy.
- These results confirm the dominance of inverse Auger scattering in graphene's early relaxation dynamics.
Conclusions:
- Inverse Auger scattering is the primary process governing hot carrier relaxation in graphene at ultrafast timescales.
- Understanding these dynamics is crucial for controlling electronic properties in solids.
- This research provides insights for developing petahertz electronics.
