Superconductivity at 19 K in Nano-Sized Bi100-xNix Alloy
Chi-Hung Lee1*, Bo-Yong Wu1, Wen-Hsien Li1, H. C. Wu2, H. D. Yang2
1Department of Physics, National Central University, Jhongli 32001, Taiwan
2Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
* presenting author:Chi-Hung Lee, email:k010211@yahoo.com.tw
Superconductivity has not been found in the ambient pressure of the bulk bismuth. However, the superconducting properties was found under the high pressure or in the amorphous film and nanowire with the transition temperatures of 8.3 K [1], 6 K [2], and 0.64 K [3], respectively. The superconducting transition temperature estimated in the BCS formalism gives an upper limit of 1.3 mK for the crystalline bismuth [4]. Here, we report on the superconductivity of the Bi100-xNix alloy nanoparticles with various Ni compositions. The superconducting transition temperature were found up to 19 K in the Bi90Ni10 nanoparticles.
The nano-sized Bi100-xNix alloys were fabricated by employing the gas-condensation method, using a chamber equipped with two decoupled evaporation sources for separate evaporation of Bi and Ni. High Resolution Transmission Electron Microscopy (HRTEM), Energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction were carried out to characterize the crystalline structure, particle size and Ni compositions of the Bi100-xNix alloy nanoparticles.
It is remarkable to find that the electronic charge distribution of Bi90Ni10 nanoparticles is significantly different from that of Bi nanoparticles. The electron density map was obtained by employing the GSAS program, followed by calculation of the inverse Fourier transforms of the structure factors to extract the electron density distribution. Possible mechanisms will be discussed in the presentation.

Reference
[1] J. Wittig, Z. Phys. 195, 228 (1966).
[2] W. Buckel et al., Z. Phys. 138, 109 (1954).
[3] Z. Ye et al, Physica B 403, 1529 (2008).
[4] Z. Mata-Pinzón et al., PLoS ONE 11, e0147645 (2016).


Keywords: Superconductivity, Nanoparticles