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Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
Published on: June 28, 2018
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Competing electronic states emerging on polar surfaces
Michele Reticcioli1,2, Zhichang Wang2,3, Michael Schmid2
1University of Vienna, Faculty of Physics, Center for Computational Materials Science, Vienna, Austria.
Nature Communications
|July 25, 2022
Summary
Excess charge on ionic surfaces forms complex electronic states, not a simple two-dimensional electron gas (2DEG). These novel surface reconstructions, including charge density waves and localized polarons, are energetically favored and impact surface properties.
Area of Science:
- Surface science
- Condensed matter physics
- Materials science
Background:
- The two-dimensional electron gas (2DEG) model is the standard for describing excess charge on polar surfaces of ionic compounds.
- This model assumes a homogeneous charge distribution confined to a few atomic layers.
Purpose of the Study:
- To investigate the nature of excess charge on the polar TaO2 termination of KTaO3(001).
- To explore alternative electronic states beyond the 2DEG model.
Main Methods:
- Utilized scanning probe microscopy (SPM) to probe surface electronic properties.
- Employed density functional theory (DFT) calculations to model and understand the observed phenomena.
Main Results:
- Identified complex electronic states, including charge density waves (CDW), electron polarons, and bipolarons, coexisting on the KTaO3(001) surface.
- Demonstrated that these reconstructed electronic states are energetically more favorable than the 2DEG model.
- Observed distinct spectroscopy signals and a local suppression of ferroelectric distortions due to these surface reconstructions.
Conclusions:
- The excess charge on polar KTaO3(001) surfaces is not a simple 2DEG but forms complex, localized electronic states.
- Electron-lattice interaction and electronic correlation drive these surface electronic reconstructions.
- These findings challenge the conventional 2DEG model and highlight new surface phenomena with implications for material properties.
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