Nernst effect and its thickness dependence in superconducting NbN films
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arXiv
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| Autores principales: | , , , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866915539371163648 |
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| author | Bouteiller, Thomas Marguerite, Arthur Daou, Ramzy Yakovlev, Dmitry Pons, Stéphane Feuillet-Palma, Cheryl Roditchev, Dimitri Fauqué, Benoît Behnia, Kamran |
| author_facet | Bouteiller, Thomas Marguerite, Arthur Daou, Ramzy Yakovlev, Dmitry Pons, Stéphane Feuillet-Palma, Cheryl Roditchev, Dimitri Fauqué, Benoît Behnia, Kamran |
| contents | Superconducting thin films and layered crystals display a Nernst signal generated by short-lived Cooper pairs above their critical temperature. Several experimental studies have broadly verified the standard theory invoking Gaussian fluctuations of a two-dimensional superconducting order parameter. Here, we present a study of the Nernst effect in granular NbN thin films with a thickness varying from 4 to 30 nm, exceeding the short superconducting coherence length and putting the system in the three-dimensional limit. We find that the Nernst conductivity decreases linearly with reduced temperature ($α_{xy}\propto \frac{T-T_c}{T_c}$), but the amplitude of $α_{xy}$ scales with thickness. While the temperature dependence corresponds to what is expected in a 2D picture, scaling with thickness corresponds to a 3D picture. We argue that this behavior indicates a 2+1D situation, in which the relevant coherence length along the thickness of the film has no temperature dependence. We find no visible discontinuity in the temperature dependence of the Nernst conductivity across T$_c$. Explaining how the response of the superconducting vortices evolves to the one above the critical temperature of short-lived Cooper pairs emerges as a challenge to the theory. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_03975 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Nernst effect and its thickness dependence in superconducting NbN films Bouteiller, Thomas Marguerite, Arthur Daou, Ramzy Yakovlev, Dmitry Pons, Stéphane Feuillet-Palma, Cheryl Roditchev, Dimitri Fauqué, Benoît Behnia, Kamran Superconductivity Superconducting thin films and layered crystals display a Nernst signal generated by short-lived Cooper pairs above their critical temperature. Several experimental studies have broadly verified the standard theory invoking Gaussian fluctuations of a two-dimensional superconducting order parameter. Here, we present a study of the Nernst effect in granular NbN thin films with a thickness varying from 4 to 30 nm, exceeding the short superconducting coherence length and putting the system in the three-dimensional limit. We find that the Nernst conductivity decreases linearly with reduced temperature ($α_{xy}\propto \frac{T-T_c}{T_c}$), but the amplitude of $α_{xy}$ scales with thickness. While the temperature dependence corresponds to what is expected in a 2D picture, scaling with thickness corresponds to a 3D picture. We argue that this behavior indicates a 2+1D situation, in which the relevant coherence length along the thickness of the film has no temperature dependence. We find no visible discontinuity in the temperature dependence of the Nernst conductivity across T$_c$. Explaining how the response of the superconducting vortices evolves to the one above the critical temperature of short-lived Cooper pairs emerges as a challenge to the theory. |
| title | Nernst effect and its thickness dependence in superconducting NbN films |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2506.03975 |