Non-Hermitian topology of quantum spin-Hall systems to detect edge-state polarization
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arXiv
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| Format: | Preprint |
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2026
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| author | Chaturvedi, Raghav Fulga, Ion Cosma Brink, Jeroen van den Hankiewicz, Ewelina M. |
| author_facet | Chaturvedi, Raghav Fulga, Ion Cosma Brink, Jeroen van den Hankiewicz, Ewelina M. |
| contents | We study the non-Hermitian topology of multi-terminal transport in a quantum spin-Hall device described by the Bernevig-Hughes-Zhang model. We show that breaking time-reversal symmetry alone does not imply non-reciprocal transport or a non-Hermitian conductance matrix. Instead, non-Hermitian topology arises only when transport becomes directionally imbalanced. We identify two distinct mechanisms that generate such a response: spin-selective coupling at the contacts and an out-of-plane Zeeman field that unbalances the counter-propagating helical edge modes. We show, for unpolarized leads, that the spin polarization-dependent response to Zeeman fields, provides a transport-based probe of the intrinsic spin polarization of the helical edge states. Moreover, we demonstrate that non-Hermitian skin effect is more sensitive than conductance elements to detect the spin polarization of the edge states. Our results clarify the conditions required for non-Hermitian topology in quantum spin-Hall transport and establish non-Hermitian skin effect as a diagnostic tool for spin-selective coupling and edge-state polarization. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_12048 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Non-Hermitian topology of quantum spin-Hall systems to detect edge-state polarization Chaturvedi, Raghav Fulga, Ion Cosma Brink, Jeroen van den Hankiewicz, Ewelina M. Mesoscale and Nanoscale Physics We study the non-Hermitian topology of multi-terminal transport in a quantum spin-Hall device described by the Bernevig-Hughes-Zhang model. We show that breaking time-reversal symmetry alone does not imply non-reciprocal transport or a non-Hermitian conductance matrix. Instead, non-Hermitian topology arises only when transport becomes directionally imbalanced. We identify two distinct mechanisms that generate such a response: spin-selective coupling at the contacts and an out-of-plane Zeeman field that unbalances the counter-propagating helical edge modes. We show, for unpolarized leads, that the spin polarization-dependent response to Zeeman fields, provides a transport-based probe of the intrinsic spin polarization of the helical edge states. Moreover, we demonstrate that non-Hermitian skin effect is more sensitive than conductance elements to detect the spin polarization of the edge states. Our results clarify the conditions required for non-Hermitian topology in quantum spin-Hall transport and establish non-Hermitian skin effect as a diagnostic tool for spin-selective coupling and edge-state polarization. |
| title | Non-Hermitian topology of quantum spin-Hall systems to detect edge-state polarization |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2602.12048 |