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Tracking Ultrafast Photocurrents in the Weyl Semimetal TaAs Using THz Emission Spectroscopy
N Sirica1, R I Tobey1,2, L X Zhao3
1Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Physical Review Letters
|May 31, 2019
Summary
Ultrafast photocurrents in Weyl semimetal TaAs are directional along the c axis and helicity-dependent in the ab plane. These findings highlight the link between crystal symmetry and optical responses in transition metal monopnictides.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid-State Physics
Background:
- Weyl semimetals like TaAs exhibit unique electronic properties due to their topological nature.
- Understanding photocurrent generation is crucial for optoelectronic applications.
Purpose of the Study:
- To investigate polarization-dependent ultrafast photocurrents in the Weyl semimetal TaAs.
- To elucidate the relationship between crystal symmetry and optical photocurrent generation.
Main Methods:
- Terahertz (THz) emission spectroscopy was employed to study transient photocurrents.
- Experiments analyzed polarization dependence of emitted THz radiation.
Main Results:
- Highly directional, transient photocurrents were observed along the noncentrosymmetric c axis, independent of light polarization.
- Helicity-dependent photocurrents were excited within the ab plane.
- Results align with static photocurrent experiments and theoretical predictions.
Conclusions:
- Optically induced photocurrents in TaAs are intrinsically linked to the crystal symmetry of transition metal monopnictides.
- The study demonstrates the role of symmetry in dictating photocurrent behavior in Weyl semimetals.
- Findings provide insights into the fundamental physics of topological materials.
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