Strong electron-phonon coupling in superconducting bismuth nanoparticles

Abstract

We report on the nanosized effect on superconducting properties of Bi nanoparticles (NPs) that extracted from the temperature and applied magnetic field dependent magnetization measurements of bismuth NPs, and revealed an enhanced TC and stronger coupling strength because of increased density of state and softened phonons ωln. A strong electron-phonon coupling (λep = 1.639) to low-lying phonons (ωln = 58 K) is found to be the leading mechanism behind the observed superconductivity with an enhanced TC ∼ 8.22 K and a strong superconducting coupling strength of α = 2.32(1) of 15 nm Bi NPs. Our results are well described by the Allen and Dynes formula within the framework of the McMillan formalism and are in agreement with the Ginzburg-Landau theory calculations.

Structural and Enhanced Optical Properties of Stabilized γ‒Bi2O3 Nanoparticles: Effect of Oxygen Ion Vacancies

“…Therefore, in this study, the synthesis of γ-Bi 2 O 3 NPs was carried out in two steps. In the first step, black colored Bi NPs were obtained using the physical vapor deposition (PVD) method, the detail of which has been given in our previous work [39]. In the second step, the as-obtained Bi NPs were annealed at 550 • C with a heating rate of 10 • C min −1 for a duration of 2 h in the air, and subsequently allowed to cool down to ambient temperature.…”

A review of superconductivity in nanostructures—from nanogranular films to anti-dot arrays

“…Two other elemental superconductors where size effects are particularly intriguing are Bi and Mo and may require separate articles to present their current status and understanding. However, for completeness, we would like to highlight that while single crystalline Bi was recently found to be superconducting with a very low T c of 0.53 mK [83], there have been several reports showing nanostructured Bi with a T c between 0.7 and 8.75 K [84]. Similarly, bulk Mo is known to show a T c of 0.915 K, but nano-crystalline films with grain sizes of 4.2 nm have reported a T c as high as 5.5 K [85].…”

“…T c is Figure 3. Variation of superconducting transition temperature with decreasing particle size (d) for elemental superconductors ([3] (Al), [30] (Nb), [34] (Pb), [62] (Ta), [82] (Sn), [84] (Bi)). defined as the temperature at which the resistance of the sample (either pellets formed from an ensemble of nanoparticles or granular films) goes below the measurable limit (zero resistance state) and is obtained from electrical transport measurements.…”

“…In many systems, like Pb, In and Sn, there is a strong competition between these two effects (QSE and SE) and the morphology of the system and structural parameters primarily dictates which of the two has the dominating influence [34,92]. A recent study on Bi nanoparticles has also shown that the effect of surface phonon softening leads to strong electron-phonon coupling, which leads to a huge enhancement of T c [84]. The electron-phonon coupling was estimated indirectly from the deviation of…”