Fabrication of Quasi-One-Dimensional Superconducting Micro- and Nanostructures

Superconducting properties of metallic nanowires can be entirely different from those of bulk superconductors because of the dominating role played by thermal and quantum fluctuations of the order parameter. For superconducting wires with diameters below $ \sim 50$ nm quantum phase slippage is an important process which can yield a non-vanishing wire resistance down to very low temperatures. Further decrease of the wire diameter, for typical material parameters down to $\sim 10$ nm, results in proliferation of quantum phase slips causing a sharp crossover from superconducting to normal behavior even at T=0. A number of interesting phenomena associated both with quantum phase slips and with the parity effect occur in superconducting nanorings. We review recent theoretical and experimental activities in the field and demonstrate dramatic progress in understanding of the phenomenon of superconductivity in quasi-one-dimensional nanostructures.Comment: 62 pages, 47 figures Misprints corrected, several equations are adapted to the experimentally relevant diffusive limi

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Evidence of quantum phase slip effect in titanium nanowires

Lehtinen

Sajavaara

Arutyunov

et al. 2012

Phys. Rev. B

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Electron transport properties of titanium nanowires were experimentally studied. Below the effective diameter 50 nm all samples demonstrated a pronounced broadening of the R(T ) dependencies, which cannot be accounted for thermal flcutuations. An extensive microscopic and elemental analysis indicates the absence of structural or/and geometrical imperfection capable to broaden the the R(T ) transition to such an extent. We associate the effect with quantum flucutuations of the order parameter.PACS numbers: 74.25.F-, 74.78.-w Since the early years of experimental studies in superconductivity it has been noticed that the supercondcunting transition R(T ) has always a finite width. Very often the broadening can be accounted for sample inhomogeneity. However, soon it became clear that, at least in low dimensional samples, the transition width remains finite even with the refined material purity and improved fabrication. The effect has been attributed to fluctuations typically more pronounced in objects with reduced dimensionality. The finite resistance R(T ) ∼ exp (−F 0 /k B T ) at a temperature T below the critical temperature T c of a quasi-one-dimensional superconducting channel with cross section σ has been explained by the thermal fluctuations of the order paprameter: the so called thermal activation of phase slips (TAPS), 1 , 2 . Here the condensation energy F 0 ∼ B 2 c ξσ of the smallest statistically independent volume ξσ, where ξ is the supercondcuting coherence length and B c is the critical magnetic field, competes with the thermal energy k B T . The effect manifests itself only sufficiently close to the critical temperature, and in extreemly homogeneous samples with micrometer-size diameter (e.g. pure whiskers) leads to the experimentally observable width of the R(T ) transition of about few mK 3 , 4 , 5 . In less homogeneous objects (e.g. lithographically fabricated nanowires) separation of the impact of the thermal fluctuations from the trivial inhomogeneity-determined R(T ) broadening is rather problematic 6 . Nevertheless with development of nanotechnology 7 it became clear that in extreemly narrow superconducting wires, with diameters ∼10 nm, the shape of the R(T ) transition by no means can be explained by sample inhomogeneity or/and thermal fluctuations 8 . The effect has been attributed to quantum fluctuations, also called -quantum phase slips (QPS) -and has been observed in a rather limited number of experiments studying the transport properties of ultra-narrow nanowires made of various superconducting materials: amorphous M oGe 9 , 10

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Fabrication of Quasi-One-Dimensional Superconducting Micro- and Nanostructures

Cited by 3 publications

References 35 publications

Experimental Study of the Fluctuation-Governed Resistive State in Quasi-One-Dimensional Superconductors

Experimental Study of the Fluctuation-Governed Resistive State in Quasi-One-Dimensional Superconductors

Superconductivity in one dimension

Evidence of quantum phase slip effect in titanium nanowires

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