Tracing the dynamics of superconducting order via transient terahertz third-harmonic generation

• Published in: Science advances 2024-03, Vol.10 (11), p.eadi7598
• Main Authors: Kim, Min-Jae, Kovalev, Sergey, Udina, Mattia, Haenel, Rafael, Kim, Gideok, Puviani, Matteo, Cristiani, Georg, Ilyakov, Igor, de Oliveira, Thales V A G, Ponomaryov, Alexey, Deinert, Jan-Christoph, Logvenov, Gennady, Keimer, Bernhard, Manske, Dirk, Benfatto, Lara, Kaiser, Stefan
• Format: Article
• Language: English
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.adi7598

Ultrafast optical control of quantum systems is an emerging field of physics. In particular, the possibility of light-driven superconductivity has attracted much of attention. To identify nonequilibrium superconductivity, it is necessary to measure fingerprints of superconductivity on ultrafast timescales. Recently, nonlinear THz third-harmonic generation (THG) was shown to directly probe the collective degrees of freedoms of the superconducting condensate, including the Higgs mode. Here, we extend this idea to light-driven nonequilibrium states in superconducting La Sr CuO , establishing an optical pump-THz-THG drive protocol to access the transient superconducting order-parameter quench and recovering on few-picosecond timescales. We show in particular the ability of two-dimensional TH spectroscopy to disentangle the effects of optically excited quasiparticles from the pure order-parameter dynamics, which are unavoidably mixed in the pump-driven linear THz response. Benchmarking the gap dynamics to existing experiments shows the ability of driven THG spectroscopy to overcome these limitations in ordinary pump-probe protocols.