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Coherent acoustic and optical phonon oscillations in Bi nanowire samples were studied with a femtosecond pump-probe technique. Laser pulses of 50 fs excited simultaneously acoustic oscillations at a frequency of about 9.5 GHz and optical phonons in the terahertz range. The transmission signal of nanowires on a glass substrate and the signal of light scattered from freestanding nanowires were measured. The acoustic velocity in nanowires was found to be close to that of bulk polycrystalline material. The changes in the optical phonon frequency at different laser fluences were simulated taking into account excitation inhomogeneity, lattice anharmonicity, diffusion, and recombination of the carriers and gave good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Current-voltage (I-V) curves have been measured on 60-μm-long Zn nanowires in contact with bulk film electrodes of Sn or Pb. The Zn nanowires become superconducting at the transition temperatures of the respectively electrodes, which are well above the transition temperature of bulk Zn. At temperatures well above the transition temperature of bulk Zn but below the transition temperatures of the electrodes, the I-V curves display a reproducible steplike pattern characteristic of the establishment of multiple localized phase-slip centers. The typical quasiparticle diffusion length associated with a phase-slip center is estimated to be 5–10 μm. These results demonstrate that the observed proximity effect occurs along the entire length of a nanowire, rather than only at the nanowire-electrode interfaces. [ABSTRACT FROM AUTHOR]

Co nanowires have been electroplated into porous Al2O3 templates. The crystalline structure and magnetic properties of Co nanowires of diameters 65 and 200 nm have been studied. Long single crystal Co segments with a hexagonal closed-packed (hcp) structure have been found in the 65 nm-thick nanowires. A mixture of face-centered cubic and hcp single crystal Co segments was observed in the 200 nm-thick nanowires. This finding suggests that the small template pore size favors the growth of hcp Co phase. Magnetic force microscopy measurements showed longitudinal spontaneous magnetic moments in the 65 nm-thick nanowires and transverse moments in the 200 nm-thick nanowires. [ABSTRACT FROM AUTHOR]