Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 47: Fluctuations, Noise and Other Transport Topics (joint session TT/DY)

TT 47.6: Talk

Thursday, March 20, 2025, 16:15–16:30, H31

Curvature-assisted high harmonic generation in strongly-driven superconductors — •Björn Niedzielski and Jamal Berakdar — Institut für Physik, Martin-Luther Universität Halle-Wittenberg, Halle/Saale 06099, Germany

Superconductors (SCs) under strong driving fields show inherently nonlinear dynamics, offering potential for nonlinear optics and high harmonic generation. However, the weak coupling of SCs to homogeneous transverse fields limits their efficiency. Here, we show that introducing curvature to mesoscopic type-II SC structures enables enhanced coupling to strong THz fields. Applied transport currents further allow for controlled emission of even and odd-order harmonic light modes.

The enhanced coupling of SCs and light arises from geometric and finite-size effects steering supercurrents while preserving the coherence of the SC state. Using the time-dependent Ginzburg-Landau framework, we simulate the dynamics of the superconducting order parameter in nanostructures with large coherence lengths under near-gap driving frequencies. Our simulations reveal the time-dependent supercurrents and their contributions to dipole radiation and high harmonic generation.

Our results highlight the role of the SC geometry and finite-size effects for amplifying nonlinear optical responses, offering a new method to use SCs for nonlinear THz optics.

Keywords: Ginzburg-Landau; High-harmonic generation; Superconductivity; Curvature