Phys.og September 22, 2022
The interplay between charge order and superconductivity remains one of the central themes of research in quantum materials. In the case of cuprates, the coupling between striped charge fluctuations and local electromagnetic fields is especially important, as it affects transport properties, coherence, and dimensionality of superconducting correlations. An international team of researchers (Germany, USA – Harvard University, Brookhaven National Laboratory, Switzerland, UK) studied the emission of coherent terahertz radiation in single-layer cuprates of the La2-xBaxCuO4 family, for which this effect is expected to be forbidden by symmetry. They found that emission vanishes for compounds in which the stripes are quasi-static but it is activated when c-axis inversion symmetry is broken by incommensurate or fluctuating charge stripes. In this case, terahertz radiation is emitted by surface Josephson plasmons, which are generally dark modes, but couple to free space electromagnetic radiation because of the stripe modulation. The work reveals coherent anomalous THz emission as a sensitive tool to probe the symmetry of superconductors in the presence of other phases. According to the researchers it should be applied to a wider class of compounds in the future, opening new possibilities for understanding the physics of complex interactions in these materials…read more. Open Access TECHNICAL ARTICLEÂ
High-temperature superconducting cuprates emit THz radiation once their surface is illuminated with ultrashort optical pulses… Credit: Jörg Harms, MPSD