• Sacépé, Benjamin
• Rogachev, Andrey

Abstract

International audience ; Finite-size scaling analysis is a well-accepted method for identification and characterization of quantum phase transitions (QPTs) in superconducting, magnetic and insulating systems. We formally apply this analysis in the form suitable for QPTs in 2-dimensional superconducting films to magnetic-field driven superconductor-metal transition in 1-dimensional MoGe nanowires. Despite being obviously inapplicable to nanowires, the 2d scaling equation leads to a high-quality scaling collapse of the nanowire resistance in the temperature and resistance ranges comparable or better to what is accepted in the analysis of the films. Our results suggest that the appearance and the quality of the scaling collapse by itself is not a reliable indicator of a QPT. We have also observed a sign-change of the zero-bias anomaly (ZBA) in the non-linear resistance, occurring exactly at the critical field of the accidental QPT. This behavior is often taken as an additional confirmation of the transition. We argue that in nanowires, the non-linearity is caused by electron heating and has no relation to the critical fluctuations. Our observation suggests that similar to the scaling collapse, the sign-change of ZBA can be a misleading indicator of QPT. Quantum phase transitions (QPT) occur at zero temperature between distinct ground states of matter; they are driven by a non-thermal parameter, g , which can be, for example, pressure or magnetic field. QPTs take place in many systems ranging from magnetic materials 1,2,3 and superconductors 4,5,6,7 to cold atoms, 8 atomic nuclei 9,10 and stars. 11 The transition from one ground state to another can be of the first order, as in the case of clean metallic ferromagnets. 12 It can also proceed by a smooth evolution of one-ground state to another over broad range of the driving parameter, as in the case of the crossover from Bardeen-Cooper-Schrieffer superconductivity to Bose-Einstein condensation. 13 But, perhaps the most interesting is the case of continuous QPTs, ...

Topics

• impedance spectroscopy
• phase
• phase transition
• superconductivity
• superconductivity