Anomalous Metallic Phase in Tunable Destructive Superconductors*

The Little-Parks effect---a flux-dependent modulation of the transition temperature in multiply connected superconductors---results from the quantization of fluxoid through holes in superconductors. In hollow superconducting cylinders with diameter smaller than the superconducting coherence length, flux-induced supercurrents can give rise to the destructive Little-Parks effect, characterized by repeated reentrant quantum phase transitions between superconducting and metallic phases. Here, we use axial and transverse magnetic fields to control the crossover between the conventional and destructive Little-Parks regimes in nanowires with an epitaxial Al shell fully surrounding InAs core. The observed dependence on flux, transverse field, temperature, and current bias is in excellent agreement with theory. Near the crossover between the conventional and destructive regimes, an anomalous metal phase is found. The anomalous metallic phase is characterized by a field-controllable, temperature-independent resistivity between adjacent superconducting lobes.

[1] https://arxiv.org/abs/1909.10654