Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 27: Focus Session: Nonlinear Spectroscopy of Collective Excitations in Quantum Magnets (joint session TT/MA)
TT 27.4: Topical Talk
Wednesday, March 19, 2025, 11:15–11:45, H36
Revealing Dynamics of Hidden Sectors with Nonlinear Spectroscopy — •Yoshito Watanabe1, Simon Trebst1, and Ciarán Hickey2,3 — 1Institute for Theoretical Physics, University of Cologne, Cologne, Germany — 2School of Physics, University College Dublin, Belfield, Dublin 4, Ireland — 3Centre for Quantum Engineering, Science, and Technology, University College Dublin, Dublin 4, Ireland
Nonlinear spectroscopy, especially in its two-dimensional coherent spectroscopy (2DCS) form, is an emerging and promising tool for studying the dynamics of quantum materials. Unlike traditional linear probes, 2DCS employs a multi-pulse approach that reveals intricate dynamics, including the ability to resolve fractional excitation continua as sharp spinon-echo signals and to study interactions between excitations, phenomena often obscured in traditional measurements.
In this work, we focus on the potential of 2DCS to detect and characterize quadrupolar excitations in quantum magnets. Using exact diagonalization and establishing an effective Hamiltonian that reflects the dynamics of hidden sectors and higher-order excitations, we identify distinct spectroscopic features, including new signatures associated with quadrupolar excitations. These results provide a guide for the experimental detection and characterization of hidden dynamics in quantum materials.
Keywords: non-linear spectroscopy; two dimensional coherent spectroscopy; quantum magnets; spin liquid