Fractional ac Josephson effect as evidence of topological hinge states in a Dirac semimetal NiTe2
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arXiv
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| Autori principali: | , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| author | Kazmin, D. Yu. Esin, V. D. Timonina, A. V. Kolesnikov, N. N. Deviatov, E. V. |
| author_facet | Kazmin, D. Yu. Esin, V. D. Timonina, A. V. Kolesnikov, N. N. Deviatov, E. V. |
| contents | We experimentally investigate Josephson current between two 5~$μ$m spaced superconducting indium leads, coupled to a NiTe$_2$ single crystal flake, which is a type-II Dirac semimetal. Under microwave irradiation, we demonstrate a.c. Josephson effect at millikelvin temperatures as a number of Shapiro steps. In addition to the integer ($n=1,2,3,4...$) steps, we observe fractional ones at half-integer values $n=1/2,3/2,5/2$ and 7/2, which corresponds to $π$ periodicity of current-phase relationship. In contrast to previous investigations, we do not observe $4π$ periodicity (disappearance of the odd $n=1,3,5...$ Shapiro steps), while the latter is usually considered as a fingerprint of helical surface states in Dirac semimetals and topological insulators. We argue, that our experiment confirms Josephson current through the topological hinge states in NiTe$_2$: since one can exclude bulk supercurrent in 5~$μ$m long Josephson junctions, interference of the hinge modes is responsible for the $π$ periodicity, while stable odd Shapiro steps reflect chiral character of the topological hinge states. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_17920 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Fractional ac Josephson effect as evidence of topological hinge states in a Dirac semimetal NiTe2 Kazmin, D. Yu. Esin, V. D. Timonina, A. V. Kolesnikov, N. N. Deviatov, E. V. Mesoscale and Nanoscale Physics Superconductivity We experimentally investigate Josephson current between two 5~$μ$m spaced superconducting indium leads, coupled to a NiTe$_2$ single crystal flake, which is a type-II Dirac semimetal. Under microwave irradiation, we demonstrate a.c. Josephson effect at millikelvin temperatures as a number of Shapiro steps. In addition to the integer ($n=1,2,3,4...$) steps, we observe fractional ones at half-integer values $n=1/2,3/2,5/2$ and 7/2, which corresponds to $π$ periodicity of current-phase relationship. In contrast to previous investigations, we do not observe $4π$ periodicity (disappearance of the odd $n=1,3,5...$ Shapiro steps), while the latter is usually considered as a fingerprint of helical surface states in Dirac semimetals and topological insulators. We argue, that our experiment confirms Josephson current through the topological hinge states in NiTe$_2$: since one can exclude bulk supercurrent in 5~$μ$m long Josephson junctions, interference of the hinge modes is responsible for the $π$ periodicity, while stable odd Shapiro steps reflect chiral character of the topological hinge states. |
| title | Fractional ac Josephson effect as evidence of topological hinge states in a Dirac semimetal NiTe2 |
| topic | Mesoscale and Nanoscale Physics Superconductivity |
| url | https://arxiv.org/abs/2404.17920 |