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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2605.08708 |
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| _version_ | 1866917483015831552 |
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| author | Paiva-Ortega, Simón Li, Hao Bittner, Eric R. Silva-Acuña, Carlos |
| author_facet | Paiva-Ortega, Simón Li, Hao Bittner, Eric R. Silva-Acuña, Carlos |
| contents | The homogeneous spectral linewidth associated with light-matter interactions is a fundamental descriptor of the optical properties of materials, governed by the quantum dynamics of the condensed-matter system. We discuss here that the homogeneous linewidth measured by means of two-dimensional electronic spectroscopy depends not only on microscopic coherence loss, but also on the observable through which the nonequilibrium dynamics are projected onto the measurement. In this Perspective, we develop a unified framework showing that changing the detection operator changes the operational definition of dephasing. For coherent emitted-field measurements, the observed linewidth largely retains its conventional connection to the optical coherence time $(T_2$). By contrast, in population-detected modalities such as photoluminescence-, photocurrent-, and other action-detected two-dimensional spectroscopies, the apparent linewidth can additionally encode excited-state population redistribution dynamics, leading naturally to an effective coherence time \(T_{2,\mathrm{eff}}\). Using a coupled-mode model propagated under a common Liouvillian, we show that identical microscopic dynamics yield distinct apparent dephasing times when projected onto coherent-emission and population-derived observables. We posit that the detection observable is not merely how a two-dimensional spectrum is measured, but part of what the spectrum fundamentally means as a materials probe. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_08708 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Detection Defines Dephasing in Two-Dimensional Electronic Spectroscopy of Materials: Coherent Field Emission versus Incoherent Population Observables Paiva-Ortega, Simón Li, Hao Bittner, Eric R. Silva-Acuña, Carlos Chemical Physics Materials Science The homogeneous spectral linewidth associated with light-matter interactions is a fundamental descriptor of the optical properties of materials, governed by the quantum dynamics of the condensed-matter system. We discuss here that the homogeneous linewidth measured by means of two-dimensional electronic spectroscopy depends not only on microscopic coherence loss, but also on the observable through which the nonequilibrium dynamics are projected onto the measurement. In this Perspective, we develop a unified framework showing that changing the detection operator changes the operational definition of dephasing. For coherent emitted-field measurements, the observed linewidth largely retains its conventional connection to the optical coherence time $(T_2$). By contrast, in population-detected modalities such as photoluminescence-, photocurrent-, and other action-detected two-dimensional spectroscopies, the apparent linewidth can additionally encode excited-state population redistribution dynamics, leading naturally to an effective coherence time \(T_{2,\mathrm{eff}}\). Using a coupled-mode model propagated under a common Liouvillian, we show that identical microscopic dynamics yield distinct apparent dephasing times when projected onto coherent-emission and population-derived observables. We posit that the detection observable is not merely how a two-dimensional spectrum is measured, but part of what the spectrum fundamentally means as a materials probe. |
| title | Detection Defines Dephasing in Two-Dimensional Electronic Spectroscopy of Materials: Coherent Field Emission versus Incoherent Population Observables |
| topic | Chemical Physics Materials Science |
| url | https://arxiv.org/abs/2605.08708 |