Experimental observation of energy-band Riemann surface
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arXiv
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866917352070709248 |
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| author | Cheng, Dali Wang, Heming Zhong, Janet Lustig, Eran Roques-Carmes, Charles Fan, Shanhui |
| author_facet | Cheng, Dali Wang, Heming Zhong, Janet Lustig, Eran Roques-Carmes, Charles Fan, Shanhui |
| contents | Non-Hermiticity naturally arises in many physical systems that exchange energy with their environment. The presence of non-Hermiticity leads to many novel topological physics phenomena and device applications. In the non-Hermitian energy band theory, the foundation of these physics and applications, both energies and wavevectors can take complex values. The energy bands thus become a Riemann surface, and such an energy-band Riemann surface underlies all the important signatures of non-Hermitian topological physics phenomena. Despite a long history and recent theoretical interests, the energy-band Riemann surface has not been experimentally studied. Here we provide a photonic observation of the energy-band Riemann surface of a non-Hermitian system. This is achieved by applying a tunable imaginary gauge transformation on the platform of the photonic synthetic frequency dimension. From the measured topology of the Riemann surface, we reveal the complex-energy winding, the open-boundary-condition spectrum, the generalized Brillouin zone, and the branch points. Our findings demonstrate a unified framework in the studies of diverse effects in non-Hermitian topological physics through an experimental observation of energy-band Riemann surfaces. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_08819 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Experimental observation of energy-band Riemann surface Cheng, Dali Wang, Heming Zhong, Janet Lustig, Eran Roques-Carmes, Charles Fan, Shanhui Optics Other Condensed Matter Non-Hermiticity naturally arises in many physical systems that exchange energy with their environment. The presence of non-Hermiticity leads to many novel topological physics phenomena and device applications. In the non-Hermitian energy band theory, the foundation of these physics and applications, both energies and wavevectors can take complex values. The energy bands thus become a Riemann surface, and such an energy-band Riemann surface underlies all the important signatures of non-Hermitian topological physics phenomena. Despite a long history and recent theoretical interests, the energy-band Riemann surface has not been experimentally studied. Here we provide a photonic observation of the energy-band Riemann surface of a non-Hermitian system. This is achieved by applying a tunable imaginary gauge transformation on the platform of the photonic synthetic frequency dimension. From the measured topology of the Riemann surface, we reveal the complex-energy winding, the open-boundary-condition spectrum, the generalized Brillouin zone, and the branch points. Our findings demonstrate a unified framework in the studies of diverse effects in non-Hermitian topological physics through an experimental observation of energy-band Riemann surfaces. |
| title | Experimental observation of energy-band Riemann surface |
| topic | Optics Other Condensed Matter |
| url | https://arxiv.org/abs/2510.08819 |