Quantum-size effect induced Andreev bound states in ultrathin metallic islands proximitized by a superconductor
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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_ | 1866911113741860864 |
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| author | Wang, Guanyong Liu, Li-Shuo Zhu, Zhen Zheng, Yue Yang, Bo Guan, Dandan Wang, Shiyong Li, Yaoyi Liu, Canhua Chen, Wei Zheng, Hao Jia, Jinfeng |
| author_facet | Wang, Guanyong Liu, Li-Shuo Zhu, Zhen Zheng, Yue Yang, Bo Guan, Dandan Wang, Shiyong Li, Yaoyi Liu, Canhua Chen, Wei Zheng, Hao Jia, Jinfeng |
| contents | While Andreev bound states (ABSs) have been realized in engineered superconducting junctions, their direct observation in normal metal/superconductor heterostructures-enabled by quantum confinement-remains experimentally elusive. Here, we report the detection of ABSs in ultrathin metallic islands (Bi, Ag, and SnTe) grown on the s-wave superconductor NbN. Using high-resolution scanning tunneling microscopy and spectroscopy, we clearly reveal in-gap ABSs with energies symmetric about the Fermi level. While the energies of these states show no position dependence, their wave functions exhibit spatial oscillations, demonstrating a quantum size effect. Both the energy levels and spatial distribution of the ABSs can be reproduced by our effective model in which a metallic island is coupled to the superconducting substrate via the proximity effect. We demonstrate that the coupling strength plays a critical role in determining the ABS energies. Our work introduces a novel physical platform for implementing ABSs, which hold promise for significant device applications. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_15184 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Quantum-size effect induced Andreev bound states in ultrathin metallic islands proximitized by a superconductor Wang, Guanyong Liu, Li-Shuo Zhu, Zhen Zheng, Yue Yang, Bo Guan, Dandan Wang, Shiyong Li, Yaoyi Liu, Canhua Chen, Wei Zheng, Hao Jia, Jinfeng Superconductivity Mesoscale and Nanoscale Physics Materials Science While Andreev bound states (ABSs) have been realized in engineered superconducting junctions, their direct observation in normal metal/superconductor heterostructures-enabled by quantum confinement-remains experimentally elusive. Here, we report the detection of ABSs in ultrathin metallic islands (Bi, Ag, and SnTe) grown on the s-wave superconductor NbN. Using high-resolution scanning tunneling microscopy and spectroscopy, we clearly reveal in-gap ABSs with energies symmetric about the Fermi level. While the energies of these states show no position dependence, their wave functions exhibit spatial oscillations, demonstrating a quantum size effect. Both the energy levels and spatial distribution of the ABSs can be reproduced by our effective model in which a metallic island is coupled to the superconducting substrate via the proximity effect. We demonstrate that the coupling strength plays a critical role in determining the ABS energies. Our work introduces a novel physical platform for implementing ABSs, which hold promise for significant device applications. |
| title | Quantum-size effect induced Andreev bound states in ultrathin metallic islands proximitized by a superconductor |
| topic | Superconductivity Mesoscale and Nanoscale Physics Materials Science |
| url | https://arxiv.org/abs/2508.15184 |