Berlin 2024 – scientific programme

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MA: Fachverband Magnetismus

MA 24: Terahertz Spintronics I

MA 24.1: Talk

Wednesday, March 20, 2024, 09:30–09:45, EB 202

Exact diagonalization study of THz two-dimensional spectroscopy in quantum magnets — •Yoshito Watanabe¹, Simon Trebst¹, and Ciarán Hickey² — ¹Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany — ²School of Physics, University College Dublin, Belfield, Dublin 4, Ireland

Two-dimensional coherent spectroscopy (2DCS) is a method used to study the nonlinear responses of systems. Recent advancements in THz generation techniques suggest the potential for 2DCS in investigating quantum magnets. This approach is theoretically proposed to discern fractionalized excitations in quantum magnets, a capability distinct from traditional linear-response methods.

Current 2DCS research often focuses on solvable models like the one-dimensional transverse field Ising model (1d-TFIM). However, there is a growing need for numerical methods that simulate 2DCS more broadly to interpret experimental data accurately.

This study addresses these methods, specifically using exact diagonalization (ED) to examine one-dimensional models. We outline ways to bridge the gap between numerical simulation results from smaller systems and experimental results typically gathered in the thermodynamic limit.

Having established the numerical techniques, we analyze how integrability-breaking terms affect the 2DCS spectra of the 1d-TFIM, which has experimental relevance to the quasi-1d spin-chain compound CoNb2O6.

Keywords: Two-Dimensional Coherent Spectroscopy; Fractionalized Excitation; Exact Diagonalization; Transverse Field Ising Model