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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2509.19255 |
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Table of Contents:
- We report evidence for high temperature superconductivity in three dimensional networks of boron doped, ultrathin carbon nanotubes (CNTs) grown inside the ~5 Angstrom channels of ZSM-5 zeolite. Confinement stabilizes (2,1) CNTs that are otherwise dynamically unstable, while boron doping shifts the Fermi level toward a van Hove singularity, as supported by ab-initio calculations. The resulting CNT network exhibits multiple, mutually consistent signatures of superconductivity at ambient pressure. DC magnetization and AC susceptibility measurements reveal the onset of a Meissner response between 220 and 250 K, with compacted samples achieving up to 93% of full diamagnetic screening. Electrical transport shows a sharp resistive transition with extrapolated Tc about 239 K and vanishing resistance in optimized samples. Specific heat measurements display a reproducible anomaly at 233 to 236 K that broadens under magnetic field, consistent with strong superconducting fluctuations. Point contact spectroscopy identifies three superconducting gaps, including a leading gap of approximately 30 meV whose temperature dependence follows BCS expectations for Tc of about 224 K, and exhibits particle-hole symmetry and Andreev reflection. Remarkably, applying pressures below 0.1 kbar enhances Tc by nearly 100 K and modulates the room temperature resistance by more than three orders of magnitude, suggesting a pressure driven 1D to 3D crossover in the CNT network. These results identify boron doped ultrathin CNT networks as a promising carbon-based platform for near ambient temperature superconductivity and reveal an unusually large pressure sensitivity with potential technological relevance.