SKM 2023 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 62: Ultrafast Dynamics of Light-Driven Systems
TT 62.5: Vortrag
Freitag, 31. März 2023, 10:45–11:00, HSZ 03
Non-equilibrium phenomena in a two-band superconductor MgB2 driven by narrow-band THz pulses — •Sergei Sobolev1, Amon Lanz1, Tao Dong2, Alexej Pashkin3, Amrit Pokharel1, Zi Zhao Gan2, Li Yu Shi2, Nan Lin Wang2, Stephan Winnerl3, Manfred Helm3, and Jure Demsar1 — 1Uni-Mainz, Mainz — 2Peking Uni., Beijing — 3HZDR, Dresden
Excitation of a superconductor (SC) with a low energy electromagnetic pulse leads to a non-equilibrium state, which may profoundly differ from a quasi-thermal one, driven by optical excitation. Such a non-equilibrium may be especially pronounced in a multi-band SC. Here, we report on systematic time-resolved studies of the dynamics of the SC order following resonant excitation with intense narrow-band THz pulses in thin films of MgB2, the prototype two-band SC with two distinct superconducting gaps. We demonstrate that the temperature and excitation density dependent dynamics qualitatively follows the behavior predicted by the phenomenological Rothwarf-Taylor model for dynamics in a single gap BCS superconductor implying strong coupling between the two condensates on the ps timescale. Tracking the dependence of the amplitude of the THz driven gap suppression, however, displays a pronounced minimum near 0.6Tc, that cannot be accounted by the phenomenological model. Comparison of the results to those obtained by excitation with NIR pulses suggests that resonant THz excitation results in long-lived (100 ps timescale) non-thermal quasiparticle distribution, which gives rise to Eliashberg-type enhancement of superconductivity, competing with pair-breaking.