Dramatic enhancement of superconductivity in single-crystalline nanowire arrays of Sn

Abstract

Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner ‘bulk’ contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state.

Experimental observation of electron-phonon coupling enhancement in Sn nanowires caused by phonon confinement effects

“…This represents an enhancement of up to 10% compared to 3.72 K, the bulk T c value. These values of T c are in agreement with the values observed in other Sn nanowire systems [10,27,28]. The second resistance drop occurs in a temperature range between 2.0 K and 2.5 K. While the first superconducting transition is related to the local superconductivity within the narrow elongated grains of the individual nanowires; we hypothesize that the second transition is related to the emergence of long-range superconductivity when coupling between these grains is established at lower temperatures.…”

A theoretical quest for high temperature superconductivity on the example of low-dimensional carbon structures

“…The slower lattice vibration allows longer electron-phonon scattering times, causing a T c is enhancement. For instance, the T c of 1D Pb nanowires (or Sn nanowires) is enhanced by a factor of ~1.6 compared to the bulk T c by this surface phonon softening effect 28 , 29 .…”

Superconducting nanoribbon with a constriction: A quantum-confined Josephson junction

“…Superconductivity is realized in atomically thin films even down to a single monolayer. Quantum size effects have been reported in atomically thin films 19 , superconducting nanoparticles 20 and islands 21 , nanowires 22 and nanowire arrays 23 . However, the low-dimensional superconductivity is strongly influenced by the imperfections such as impurities, disorder and structural defects 24 .…”