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Coherent emission from surface Josephson plasmons in striped cuprates
D Nicoletti1, M Buzzi1, M Fechner1
1Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany.
Summary
Terahertz radiation emission in cuprates is forbidden by symmetry but activated by fluctuating charge stripes. This occurs when c-axis inversion symmetry is broken, enabling surface Josephson plasmons to couple to electromagnetic radiation.
Area of Science:
- Quantum Materials Science
- Condensed Matter Physics
- Superconductivity Research
Background:
- The relationship between charge order and superconductivity is a key area in quantum materials research.
- In cuprates, striped charge fluctuations significantly influence transport properties and superconducting correlations.
- Understanding these interactions is crucial for developing novel quantum devices.
Purpose of the Study:
- To investigate the emission of coherent terahertz radiation in single-layer cuprates (La2-xBaxCuO4).
- To explore the conditions under which terahertz emission, expected to be symmetry-forbidden, can be activated.
- To elucidate the role of charge stripe dynamics in enabling this emission.
Main Methods:
- Experimental study of terahertz radiation emission in La2-xBaxCuO4 single-layer cuprates.
- Analysis of compounds with varying charge stripe characteristics (quasi-static vs. fluctuating).
- Investigation of symmetry breaking, specifically c-axis inversion symmetry.
Main Results:
- Terahertz emission was found to vanish in compounds with quasi-static charge stripes.
- Emission was activated in compounds with incommensurate or fluctuating charge stripes, such as La1.905Ba0.095CuO4 and La1.845Ba0.155CuO4.
- This activation is linked to the breaking of c-axis inversion symmetry.
Conclusions:
- Fluctuating charge stripes and broken c-axis inversion symmetry are essential for terahertz radiation emission in these cuprates.
- Surface Josephson plasmons, normally dark modes, couple to free space radiation due to stripe modulation.
- This finding offers new insights into the interplay of charge order, superconductivity, and electromagnetic phenomena in quantum materials.
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