Gapless superconductivity in the low-frequency electrodynamic response of two-dimensional granular In/InO$_x$ composites
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| Format: | Preprint |
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2024
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| _version_ | 1866914820762107904 |
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| author | Zhang, Xinyang Wu, Jinze Palevski, Alexander Kapitulnik, Aharon |
| author_facet | Zhang, Xinyang Wu, Jinze Palevski, Alexander Kapitulnik, Aharon |
| contents | We measured the full complex ac conductance of two-dimensional granular In/InO$_x$ composites using the mutual inductance technique to explore the transition from a "failed-superconductor-turned anomalous metal" to a robust superconductor. In this system, room-temperature annealing was adopted to tune the InO$_x$-mediated coupling between In grains, allowing for the observation of both a "true" superconductor-to-insulator transition and the emergence of an intervening anomalous metallic state. In this paper, we show that further annealing increases the inter-grain coupling, which eliminates the anomalous metallic phase, but at the same time prevent the emergence of strong Bose-dominated insulating phase. The complex ac conductance revealed a $T\to0$ saturating dissipative response in a finite magnetic field, coexisting with a robust superfluid density. The anomalous power-law spectra for the dissipative response appear to indicate quantum critical behavior proximate to a quantum superconductor to anomalous-metal transition as probed in the kilo-Hertz range, and point to signatures of gapless superconductivity in our granular superconducting system. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_00900 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Gapless superconductivity in the low-frequency electrodynamic response of two-dimensional granular In/InO$_x$ composites Zhang, Xinyang Wu, Jinze Palevski, Alexander Kapitulnik, Aharon Superconductivity We measured the full complex ac conductance of two-dimensional granular In/InO$_x$ composites using the mutual inductance technique to explore the transition from a "failed-superconductor-turned anomalous metal" to a robust superconductor. In this system, room-temperature annealing was adopted to tune the InO$_x$-mediated coupling between In grains, allowing for the observation of both a "true" superconductor-to-insulator transition and the emergence of an intervening anomalous metallic state. In this paper, we show that further annealing increases the inter-grain coupling, which eliminates the anomalous metallic phase, but at the same time prevent the emergence of strong Bose-dominated insulating phase. The complex ac conductance revealed a $T\to0$ saturating dissipative response in a finite magnetic field, coexisting with a robust superfluid density. The anomalous power-law spectra for the dissipative response appear to indicate quantum critical behavior proximate to a quantum superconductor to anomalous-metal transition as probed in the kilo-Hertz range, and point to signatures of gapless superconductivity in our granular superconducting system. |
| title | Gapless superconductivity in the low-frequency electrodynamic response of two-dimensional granular In/InO$_x$ composites |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2406.00900 |