Suppression of superconductivity in thin Nb nanowires fabricated in the vortex cores of superfluid helium

Highlights: • Laser ablation in superfluid helium allows producing thin nanowires of any metal. • Nb nanowires, about 4 nm in diameter, form in the cores of superfluid vortices. • Our oxide-free Nb nanowires exhibit a quantum superconductor-to-insulator transition. • The insulating behavior in Nb wires is explained in terms of quantum phase slips. • Such nanowires can be used in superconducting phase-slip qubits and transistors. - Abstract: Nanowires of niobium, platinum and indium–lead In₈₈Pb₁₂ alloy with diameters of 4.2, 3.6 and 8 nm, respectively, were grown in quantized vortices of superfluid helium, and the dependences of their resistance on temperature have been studied. Through a detailed comparison of these dependences we present evidence that superconducting niobium wires allow a high rate of quantum phase slip. This phase slippage leads to a phase transition to an insulating state at T → 0