Quantum breakdown of superconductivity in low-dimensional materials

The breakdown of superconductivity is described as a reduction in the amplitude of the order parameter or a breakdown in phase coherence of Cooper pairs. This Review Article highlights recent results that show both mechanisms may be at play simultaneously. In order to understand the emergence of superconductivity it is useful to study the reverse process and identify the various pathways that lead to its destruction. One way is to increase the amount of disorder, as this leads to an increase in Coulomb repulsion that overpowers the attractive interaction responsible for Cooper pair formation. A second pathway-applicable to uniformly disordered materials-is to utilize the competition between superconductivity and Anderson localization, as this leads to electronic granularity in which phase and amplitude fluctuations of the superconducting order parameter play a role. Finally, a third pathway is to construct an array of superconducting islands coupled by some form of proximity effect that leads from a superconducting state to a state with finite resistivity, which appears like a metallic groundstate. This Review Article summarizes recent progress in understanding of these different pathways, including experiments in low dimensional materials and application in superconducting quantum devices.