Absence of superconductivity in micrometer-sized ɛ-NbN single crystals
Fan-Yun Chiu, Tsu-Lien Hung, Cheng-Yen Liu, Ya-Hsin Pai, Wei-Liang Chien, Peng-Jen Chen, Ting-Kuo Lee, Ming-Jye Wang, Min-Nan Ou, Chang C. Tsuei, Maw-Kuen Wu, Chia-Seng Chang, Yang-Yuan Chen
DOI 10.1103/PhysRevB.105.174512 · Physical Review B
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Abstract
It is important to study the properties of high quality single crystal in order to resolve the issue of an interesting material in which certain debatable fundamental properties exist. However, it is unfortunate that a sizable single crystal for experimental measurements is not always available. NbN is one of the examples; it has attracted scientific and engineering interest due to its diverse physical properties and a variety of structural phases. Until now superconductivity is only observed in cubic δ- and tetragonal γ-NbN but not in hexagonal ɛ-NbN. Recently, Zou et al. reported the observation of superconductivity with Tc∼11.6K in a hexagonal ɛ-NbN based on the measurement on a multiphase powder specimen. In order to resolve the issue, the work used the electron backscattering diffraction technique to characterize phases of micron-size NbN crystals from commercial powders and measure their transport properties. Our results unambiguously confirm that the hexagonal ɛ-NbN phase is not superconducting.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NbN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 13.6 | Pressure not reported | onset |
| NbN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 11.2 | Pressure not reported | midpoint |
| NbN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 12.8 | Pressure not reported | onset |
| NbN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 11.6 | Pressure not reported | unknown |
| NbN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 18.2 | Pressure not reported | unknown |
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