Size effect of strong-coupled superconducting In2Bi nanoparticles: An investigation of short-range electron phonon coupling

We report the influence of the nanosized effect on the superconducting properties of bimetallic In2Bi nanoparticles. In this study, the temperature- and applied magnetic field-dependence of the magnetization were utilized to investigate the electron-phonon coupling effect while controlling particle sizes < d > from 21(2) to 42(5) nm. As the particle size decreases, the electron-phonon constant lambda(EP) decreases rapidly, signaling the short-range electron-phonon coupling effect which acts to confine the electrons within a smaller volume, thereby giving rise to a higher superconducting transition temperature T-C. An enhanced superconducting transition was observed from the temperature dependence of magnetization, revealing a main diamagnetic Meissner state below T-C similar to 5.72(5) K for < d > similar to 31(1) nm In2Bi nanoparticles. The variation of the T-C is very sensitive to the particle size, which might be due to crystallinity and size uniformity of the samples. The electron-phonon coupling to low lying phonons is found to be the leading mechanism for the observed strong-coupling superconductivity in the In2Bi system. (C) 2015 AIP Publishing LLC.