Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Correlated Magnetism – Dynamics and Spectroscopy

TT 33.2: Talk

Tuesday, March 10, 2026, 11:15–11:30, HSZ/0105

Third-Order Nonlinear Response in Frustrated Magnets: Efficient Calculation in the Frequency Domain — •Marius Möller, Roser Valentí, and David A.S. Kaib — Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany

Techniques measuring higher-order response functions, such as two-dimensional coherent spectroscopy (2DCS) were proposed as powerful tools to provide deeper insights into the excitations of a system. However, calculating nonlinear response functions can be computationally intensive. Recently, we proposed an efficient Lanczos-based approach to calculate the second order susceptibility χ²(ω_t,ω_τ) [1]. Here, we present different approaches and approximations to compute the more commonly probed third-order susceptibilities χ³ (ω_t,ω_τ) directly in the frequency domain. We compare them in terms of convergence, numerical stability and computational cost. Finally, we apply these techniques to frustrated magnets.

M.M., D.K. and R.V. gratefully acknowledge funding by the DFG (German Research Foundation): TRR 288-422213477.
[1] D.A.S. Kaib, M. Möller, R. Valentí, arXiv:2502.01746 (2025.

Keywords: Two-dimensional Coherent Spectroscopy (2DCS); Nonlinear Response; Exact Diagonalization