Dynamical interplay between superconductivity and pseudogap in cuprates as revealed by terahertz third-harmonic generation spectroscopy.

ABSTRACT: We report on nonlinear terahertz third-harmonic generation (THG) measurements on YBa₂Cu₃O_6+x thin films. Different from conventional superconductors, the THG signal starts to appear in the normal state, which is consistent with the crossover temperature T* of pseudogap over broad doping levels. Upon lowering the temperature, the THG signal shows an anomaly just below T_c 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 T_c, couples to the mode already developed below T^*, resulting in an energy level splitting. However, this coupling effect is not evident in un

SUBMITTER: Yuan J 

PROVIDER: S-EPMC10857425 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature