Vortex-driven superconducting diode effect in asymmetric multilayer heterostructures

Abstract

The superconducting diode effect (SDE), characterized by nonreciprocal critical currents, has attracted growing attention due to its potential applications in quantum technologies and energy-efficient devices. In this work, we explore the microscopic mechanism of the SDE by simulating asymmetric multilayer heterostructures within time-dependent Ginzburg-Landau theory. We systematically vary the layer thickness, external magnetic field and stacking order in a trilayer structure composed of niobium, vanadium, and tantalum, which share a similar structure to that in the pioneering experimental work, to clarify the role of vortex dynamics. Our simulations reveal a pronounced SDE originating from the interplay of Lorentz forces and asymmetric vortex dynamics, which strongly depend on layer stacking order. Besides, by simply changing the stacking order of the constituent layers, the SDE can be entirely suppressed. These findings offer insights into the microscopic mechanisms of the SDE and provide a feasible approach for controlling and eliminating the SDE in practical superconducting devices.

Figures (10)

• Figure 1: Illustration of the multilayer superconducting structure. A three-dimensional schematic of the superconducting sample, shown as a blue cuboid. A yellow arrow indicates the direction of the applied external current $\mathbf{j_\mathrm{ext}}$ along the $x$-axis, and a green arrow indicates the direction of the external magnetic field $\mathbf{H_\mathrm{ext}}$ along the $y$-axis. The coordinate axes are shown in black. The enlarged view of the periodic layered structure highlighted by the dashed circle is shown as color-coded, with red representing niobium, yellow denoting vanadium, and blue being tantalum.
• Figure 2: Critical current and superconducting diode efficiency in a 3-cycle periodic layer stack.(a) Critical current $\lvert j_\mathrm{c}^\pm \rvert$ as a function of the external magnetic field. The red line and blue line correspond to the positive and negative current directions ($\pm j$), respectively, and the vertical axis shows the magnitude of the critical current in each case. (b) Superconducting diode efficiency $\eta$ as a function of the external magnetic field. The black line indicates the efficiency. All curves are obtained for the multilayer sample at a bath temperature of $T_0 = 4.00$ K.
• Figure 3: Current–resistance behavior and Cooper-pair density distributions in a 3-cycle periodic layer stack.(a) Current–resistance characteristics of the sample at a bath temperature of $T_0 = 4.0~\mathrm{K}$ and an external magnetic field of $H_\mathrm{ext} = 0.08H_\mathrm{c2}$. The resistance is normalized by the normal-state resistance $R_\mathrm{n}$. The red line corresponds to the positive current direction ($+j$) and the blue line corresponds to the negative current direction ($-j$). Points labelled I, II, and III on the red curve and I$'$ , II$'$ , and III$'$ on the blue curve mark representative states used in the (c), where the applied currents have equal magnitude but opposite directions. (b) Distributions of the Cooper-pair density for the states indicated in (a). Colors represent the magnitude of the density, with blue indicating low values and yellow indicating high values along the color bar. (c) Cooper-pair density distributions during the phase transition for positive and negative current directions. The full phase-transition process is provided in Supplementary Movie 1.
• Figure 4: Free-energy distributions during the phase transition. Free-energy $\mathcal{F}$ distributions during the phase transition for the positive and negative current directions ($\pm j$). Colors indicate the magnitude of the free energy, with blue representing low values and red representing high values along the color bar. The two distributions correspond to the states shown in (c) of Fig. 3.
• Figure 5: Current–resistance behavior and Cooper-pair density distributions at higher magnetic field.(a) Current–resistance characteristics of the sample at a bath temperature of $T_0 = 4.0~\mathrm{K}$ and an external magnetic field of $H_\mathrm{ext} = 0.32H_\mathrm{c2}$. The resistance is normalized by the normal-state resistance $R_\mathrm{n}$. The red line corresponds to the positive current direction ($+j$) and the blue line corresponds to the negative current ($-j$) direction. Points labelled I, II, and III on the red line and I$'$, II$'$, and III$'$ on the blue line indicate representative states used in the (c), where the applied currents have equal magnitude but opposite sign. (b) Distributions of the Cooper-pair density for the states marked in (a). Colors represent the magnitude of the density, with blue indicating low values and yellow indicating high values along the color bar. (c) Cooper-pair density distributions during the phase transition for the positive and negative current directions. The complete phase-transition process is shown in Supplementary Movie 2.