Dynamical interplay between superconductivity and pseudogap in cuprates as revealed by terahertz third-harmonic generation spectroscopy.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38335284.
- Also identified by DOI 10.1126/sciadv.adg9211 and PMC identifier 10857425.
- Licence recorded as CC BY-NC.
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Abstract
We report on nonlinear terahertz third-harmonic generation (THG) measurements on YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+<i>x</i></sub> thin films. Different from conventional superconductors, the THG signal starts to appear in the normal state, which is consistent with the crossover temperature <i>T</i>* of pseudogap over broad doping levels. Upon lowering the temperature, the THG signal shows an anomaly just below <i>T</i><sub>c</sub> in the optimally doped sample. Notably, we observe a beat pattern directly in the measured real-time waveform of the THG signal. We elaborate that the Higgs mode, which develops below <i>T</i><sub>c</sub>, couples to the mode already developed below <i>T<sup>*</sup></i>, resulting in an energy level splitting. However, this coupling effect is not evident in underdoped samples. We explore different potential explanations for the observed phenomena. Our research offers valuable insight into the interplay between superconductivity and pseudogap.