The superconducting diode effect has recently been reported in a variety of systems and different symmetry-breaking mechanisms have been examined. However, the frequency range of these potentially important devices still remains obscure. We investigated superconducting microbridges of Nb3Sn in out-of-plane magnetic fields; optimum magnetic fields of ∼10 mT generate ∼10% diode efficiency, while higher fields of ∼15–20 mT quench the effect. The diode changes its polarity with magnetic field reversal. We documented superconductive diode rectification at frequencies up to 100 kHz, the highest reported as of today. Interestingly, the bridge resistance during diode operation reaches a value that is a factor of two smaller than in its normal state, which is compatible with the vortex-caused mechanism of resistivity. This is confirmed by finite-element modeling based on time-dependent Ginzburg-Landau equations. To explain experimental findings, no assumption of lattice thermal inequilibrium has been required. Dissimilar edges of the superconductor strip can be responsible for the inversion symmetry breaking by the vortex penetration barrier; visual evidence of this opportunity was revealed by scanning electron microscopy. Estimates are in favor of a much higher (GHz) range of frequencies for this type of diode.
S. Chahid, S. Teknowijoyo, I. Mowgood, and A. Gulian, High-frequency diode effect in superconducting Nb3Sn microbridges, Phys. Rev. B 107, 054506 (2023). https://doi.org/10.1103/PhysRevB.107.054506
This video provides additional information related to Fig. 4 and Fig. 5 of the Main Text. The blue moving asterisk indicates the current evolution at the given moment of time in accordance with the formula sin(omega t+pi). Each moment of time is being typed in at the left top corner of the upper panel. The total evolution time corresponds to 2 periods of oscillation with the frequency omega=0.005. The top panel corresponds to the active part of the bridge. Its color indicates normalized Cooper pair density in accordance to the color coding shown in the left. Driven by the Lorentz force exerted by the current, the vortices/flux quanta appear and propagate across the bridge. This generates voltage spikes shown in the bottom panel. Only penetration through the top edge is allowed since the Bean-Livingston barrier is lower at that edge due to the weaker Cooper-pair density (broken IS), as the color coding demonstrates. Attempts for vortex nucleation at the bottom edge when the current changes its polarity, are unsuccessful: only periodic color change goes on. In absence of moving vortices, the resistance is absent: the voltage is close to zero, as the black curve in the bottom panel indicates.
American Physical Society
This article was originally published in Physical Review B, volume 107, in 2023. https://doi.org/10.1103/PhysRevB.107.054506