Superconductivity in one dimension

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.