Charge transfer empties the flat band in 4H$_b$-TaS$_2$ -- except at the 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_ | 1866911116771196928 |
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| author | Date, Mihir Bae, Hyeonhu Louat, Alex Domaine, Gabriele Schröter, Niels B. M. Da Como, 2 Enrico Yan, Binghai Watson, Matthew D. |
| author_facet | Date, Mihir Bae, Hyeonhu Louat, Alex Domaine, Gabriele Schröter, Niels B. M. Da Como, 2 Enrico Yan, Binghai Watson, Matthew D. |
| contents | The 4H\textsubscript{b} polytype of TaS$_2$ is a natural heterostructure of H and T-type layers. Intriguing recent evidence points towards a possibly chiral superconducting ground state, unlike the superconductivity found in other polytypes where the T layers are absent, requiring understanding of the possible contributions of electrons from the T layers. Here we use micro-focused angle resolved photoemission spectroscopy to reveal that the T termination of the 4H\textsubscript{b} structure is metallic, but a subsurface T layer -- seen below an H termination and thus more representative of the bulk case -- is gapped. The results imply a complete charge transfer of 1 electron per 13 Ta from the T to adjacent H layers in the bulk, but an incomplete charge transfer at the T termination, yielding a metallic Fermi surface with a planar-chiral character. A similar metallic state is found in an anomalous region with likely T-H-H' stacking at the surface. Our results exclude cluster Mott localisation in either the bulk or surface of 4H$_b$-TaS$_2$ and point to a scenario of superconductivity arising from Josephson-like tunneling between the H layers. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_16411 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Charge transfer empties the flat band in 4H$_b$-TaS$_2$ -- except at the surface Date, Mihir Bae, Hyeonhu Louat, Alex Domaine, Gabriele Schröter, Niels B. M. Da Como, 2 Enrico Yan, Binghai Watson, Matthew D. Superconductivity Strongly Correlated Electrons The 4H\textsubscript{b} polytype of TaS$_2$ is a natural heterostructure of H and T-type layers. Intriguing recent evidence points towards a possibly chiral superconducting ground state, unlike the superconductivity found in other polytypes where the T layers are absent, requiring understanding of the possible contributions of electrons from the T layers. Here we use micro-focused angle resolved photoemission spectroscopy to reveal that the T termination of the 4H\textsubscript{b} structure is metallic, but a subsurface T layer -- seen below an H termination and thus more representative of the bulk case -- is gapped. The results imply a complete charge transfer of 1 electron per 13 Ta from the T to adjacent H layers in the bulk, but an incomplete charge transfer at the T termination, yielding a metallic Fermi surface with a planar-chiral character. A similar metallic state is found in an anomalous region with likely T-H-H' stacking at the surface. Our results exclude cluster Mott localisation in either the bulk or surface of 4H$_b$-TaS$_2$ and point to a scenario of superconductivity arising from Josephson-like tunneling between the H layers. |
| title | Charge transfer empties the flat band in 4H$_b$-TaS$_2$ -- except at the surface |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2508.16411 |