Phase-driven collapse of the Cooper condensate in a nanosized superconductor

Abstract

Superconductivity can be understood in terms of a phase transition from an uncorrelated electron gas to a condensate of Cooper pairs in which the relative phases of the constituent electrons are coherent over macroscopic length scales. The degree of correlation is quantified by a complex-valued order parameter, whose amplitude is proportional to the strength of the pairing potential in the condensate. Supercurrent-carrying states are associated with non-zero values of the spatial gradient of the phase. The pairing potential and several physical observables of the Cooper condensate can be manipulated by means of temperature, current bias, dishomogeneities in the chemical composition or application of a magnetic field. Here we show evidence of complete suppression of the energy gap in the local density of quasiparticle states (DOS) of a superconducting nanowire upon establishing a phase difference equal to pi over a length scale comparable to the superconducting coherence length. These observations are consistent with a complete collapse of the pairing potential in the center of the wire, in accordance with theoretical modeling based on the quasiclassical theory of superconductivity in diffusive systems. Our spectroscopic data, fully exploring the phase-biased states of the condensate, highlight the profound effect that extreme phase gradients exert on the amplitude of the pairing potential. Moreover, the sharp magnetic response observed near the onset of the superconducting gap collapse regime can be exploited to realize ultra-low noise magnetic flux detectors.

7 pages, 5 color figures plus supporting info

References in corpus (8)

• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• The Josephson heat interferometer
• Rectification of electronic heat current by a hybrid thermal diode
• Imaging of super-fast dynamics and flow instabilities of superconducting vortices
• Phase controlled superconducting proximity effect probed by tunneling spectroscopy
• Proximity DC squids in the long junction limit
• Highly-sensitive superconducting quantum interference proximity transistor
• Spectral characteristics of a fully-superconducting SQUIPT

Cited by in corpus (15)

• Preliminary demonstration of a persistent Josephson phase-slip memory cell with topological protection
• Phase-tunable thermal rectification in the topological SQUIPT
• Thermal superconducting quantum interference proximity transistor
• Josephson photodetectors via temperature-to-phase conversion
• A Topological SQUIPT based on helical edge states in proximity to superconductors
• High operating temperature in V-based superconducting quantum interference proximity transistors
• Phase-Controllable Nonlocal Spin Polarization in Proximitized Nanowires
• Ultra linear magnetic flux-to-voltage conversion in superconducting quantum interference proximity transistors
• Inductive Superconducting Quantum Interference Proximity Transistor: the L-SQUIPT
• Magnetometry with low resistance proximity Josephson junction
• Noise of a superconducting magnetic flux sensor based on a proximity Josephson junction
• Flux pumping of Cooper pairs through a Josephson Energy-Suppression Pump
• Single charge transport in a fully superconducting SQUISET locally tuned by self-inductance effects
• Phase relations in superconductor-normal metal-superconductor tunnel junctions
• Boundary conditions for the order parameter and the proximity influenced internal phase differences in double superconducting junctions