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Correlations among superconductivity, structural instability, and band filling in Nb1-xB2 at the critical point x=0.2

R. J. Xiao·K. Q. Li·H. X. Yang·G. C. Che·H. R. Zhang·C. Ma·Z. X. Zhao·J. Q. Li
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Abstract

We performed an extensive investigation on the correlations among superconductivity, structural instability and band filling in Nb1-xB2 materials. Structural measurements reveal that a notable phase transformation occurs at x=0.2, corresponding to the Fermi level (EF) in the pseudogap with the minimum total density of states (DOS) as demonstrated by the first-principles calculations. Superconductivity in Nb1-xB2 generally becomes visible in the Nb-deficient materials with x=0.2. Electron energy-loss spectroscopy (EELS) measurements on B K-edge directly demonstrated the presence of a chemical shift arising from the structural transformation. Our systematical experimental results in combination with theoretical analysis suggest that the emergence of hole states in the sigma-bands plays an important role for understanding the superconductivity and structural transition in Nb1-xB2.

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R. J. Xiao, K. Q. Li, H. X. Yang, G. C. Che, H. R. Zhang, C. Ma, Z. X. Zhao, J. Q. Li. 2006-03-27. Correlations among superconductivity, structural instability, and band filling in Nb1-xB2 at the critical point x=0.2. https://doi.org/10.1103/physrevb.73.224516

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