Theory of Nonlinear Spectroscopy of Quantum Magnets
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arXiv
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| Hauptverfasser: | , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866916628819607552 |
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| author | Srivastava, Anubhav Birnkammer, Stefan Sim, GiBaik Knap, Michael Knolle, Johannes |
| author_facet | Srivastava, Anubhav Birnkammer, Stefan Sim, GiBaik Knap, Michael Knolle, Johannes |
| contents | Two-dimensional coherent spectroscopy (2DCS) is an established method for characterizing molecules and has been proposed in the THz regime as a new tool for probing exotic excitations of quantum magnets; however, the precise nature of the coupling between pump field and spin degrees of freedom has remained unclear. Here, we develop a general response theory of 2DCS and show how magneto-electric as well as polarization couplings contribute to 2DCS in addition to the typically assumed magnetization. We propose experimental protocols to distill individual contributions, for instance from exchange-striction or spin current mechanism, when the electric field couples to terms quadratic in spin operators. We provide example calculations for the paradigmatic twisted Kitaev chain material $\mathrm{CoNb}_{2}\mathrm{O}_{6}$ and highlight the crucial role of contributions from cross-coupling between polarization and magnetic nonlinear susceptibilities. Our work paves the way for systematic studies of light-matter couplings in quantum magnets and for establishing 2DCS as a versatile tool for probing fractional excitations of exotic magnetic quantum phases. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_17554 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Theory of Nonlinear Spectroscopy of Quantum Magnets Srivastava, Anubhav Birnkammer, Stefan Sim, GiBaik Knap, Michael Knolle, Johannes Strongly Correlated Electrons Two-dimensional coherent spectroscopy (2DCS) is an established method for characterizing molecules and has been proposed in the THz regime as a new tool for probing exotic excitations of quantum magnets; however, the precise nature of the coupling between pump field and spin degrees of freedom has remained unclear. Here, we develop a general response theory of 2DCS and show how magneto-electric as well as polarization couplings contribute to 2DCS in addition to the typically assumed magnetization. We propose experimental protocols to distill individual contributions, for instance from exchange-striction or spin current mechanism, when the electric field couples to terms quadratic in spin operators. We provide example calculations for the paradigmatic twisted Kitaev chain material $\mathrm{CoNb}_{2}\mathrm{O}_{6}$ and highlight the crucial role of contributions from cross-coupling between polarization and magnetic nonlinear susceptibilities. Our work paves the way for systematic studies of light-matter couplings in quantum magnets and for establishing 2DCS as a versatile tool for probing fractional excitations of exotic magnetic quantum phases. |
| title | Theory of Nonlinear Spectroscopy of Quantum Magnets |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2502.17554 |