Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 66: Ultrafast Dynamics of Light-Driven Systems
TT 66.1: Hauptvortrag
Freitag, 5. April 2019, 09:30–10:00, H2
Non-equilibrium superconductivity: from post-quench dynamics to controlling competing orders — •Peter P. Orth — Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
Understanding and controlling the non-equilibrium behavior of correlated quantum systems is one of the major research goals in condensed matter physics. It holds promise to dynamically tune material properties on ultrafast timescales. One route to optical control of correlated matter is via excitation of optical phonons. Another avenue is to excite acoustic phonons, which, due to their low excitation energies, generally leads to less heating. We demonstrate that driving acoustic phonons to a non-equilibrium state results in the remarkable phenomenon of a momentum-dependent effective temperature, by which electronic states at different regions of the Fermi surface are subject to distinct local temperatures. This has a profound effect on the delicate balance between competing ordered states in unconventional superconductors, opening a new avenue to control correlated phases. We also report on a joint theory-experiment study of THz pump-probe spectroscopy of superconductors Nb3Sn and NbN. To quantitatively describe the superconducting gap dynamics, we present a semi-phenomenological approach that captures not only the coherent BCS gap dynamics at sub-picosecond timescales but also dissipative processes beyond BCS. Finally, we explore gap dynamics in two-band systems, where we find that the presence of two gap scales leads to the appearance of a new exponent in the universal power-law decay of the oscillations.