Abstract
We demonstrate that superconducting aluminium nano-bridges can be driven into a state with complete suppression of the critical supercurrent via electrostatic gating. Probing both in- and out-of-plane magnetic field responses in the presence of electrostatic gating can unveil the mechanisms that primarily cause the superconducting electric field effects. Remarkably, we find that a magnetic field, independently of its orientation, has only a weak influence on the critical electric field that identifies the transition from the superconducting state to a phase with vanishing critical supercurrent. This observation points to the absence of a direct coupling between the electric field and the amplitude of the superconducting order parameter or $2\pi$-phase slips via vortex generation. The magnetic field effect observed in the presence of electrostatic gating is described within a microscopic model where a spatially uniform inter-band $\pi$-phase is stabilized by the electric field. Such an intrinsic superconducting phase rearrangement can account for the suppression of the supercurrent, as well as for the weak dependence of the critical magnetic fields on the electric field.
Highlights
It has been shown that the superconducting (SC) properties of metallic Bardeen-Cooper-Schrieffer (BCS) superconductors can be influenced via electrostatic gating [1]
We find that the magnetic field has only a weak influence on the electric field effect in the SC bridges. This phenomenology is starkly independent of the magnetic field orientation, despite the very different interactions between SC thin films and in- and out-of-plane magnetic fields. These findings suggest the absence of a direct electric coupling between the electric field and the amplitude of the SC order parameter, or 2π phase slips generated by vortices
Comparing the above theoretical results with the experimental observations we argue that the experimental outcome supports the π phase for accounting the phenomenology of the magnetic field response of the SC nanobridges in the presence of an electrostatic gating
Summary
It has been shown that the superconducting (SC) properties of metallic Bardeen-Cooper-Schrieffer (BCS) superconductors can be influenced via electrostatic gating [1]. Recent experiments have probed the effect of electrostatic gating on the SC phase in a SQUID [10], and on the nature of the switching current distributions in gated titanium Dayem bridges [11]. While these observations clearly indicate that the electric field can suppress the supercurrent, whether and how it acts on the amplitude or the phase of the SC order parameter are questions so far unanswered. In thin films BZ generally leads to screening currents and a spatially varying order parameter, marked by 2π -phase slips, as flux
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