Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 71: Ultrafast Phenomena

TT 71.4: Vortrag

Donnerstag, 12. März 2026, 10:15–10:30, HSZ/0103

Two-dimensional coherent spectroscopy of multiband superconductor — •Silvia Neri — Max Planck for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart

An intriguing question in superconductivity is how to efficiently detect signatures of the collective excitations associated with the superconducting order parameter. The features associated with collective modes can indeed provide insight into various aspects of the superconducting state. We address this question by theoretically modeling a 2D THz pump probe spectroscopy experiment for a two-band superconductor. Two-dimensional spectroscopy is a powerful method with wide applications, from rovibronic excitations in biomolecular systems to magnons in antiferromagnets, and it has been recently applied to superconducting collective modes [1]. To numerically compute the dynamics of our model, we adopt a pseudospin description and choose realistic parameters for both the pulses and the superconducting state, reflective of MgB₂. The numerically evaluated 2D spectrum shows, in addition to the first- and third-harmonic signals, the presence of sidebands associated with the Leggett-mode frequency of the system. We then derive an analytical expression for the nonlinear current to identify the process responsible for this numerical finding. Our results suggest that applying 2D techniques to superconductors offers a promising route for exploring their collective dynamics.
[1] A. Dutta et al., J. Phys.: Condens. Matter 37, 203002 (2025)

Keywords: THz spectroscopy; 2D coherent spectroscopy; collective modes; Leggett mode; multiband superconductors