Field-Free Superconducting Diode in a Magnetically Nanostructured Superconductor

Ji Jiang, M.V. Milošević, Yong-Lei Wang, Zhi-Li Xiao, F.M. Peeters, and Qing-Hu Chen

Phys. Rev. Applied 18, 034064 – Published 23 September 2022

Abstract

A strong superconducting diode effect (SDE) is revealed in a thin superconducting film periodically nanostructured with magnetic dots. The SDE is caused by the current-activated dissipation mitigated by vortex-antivortex pairs (VAPs), which periodically nucleate under the dots, move and annihilate in the superconductor—eventually driving the system to the high-resistive state. Inversing the polarity of the applied current destimulates the nucleation of VAPs, the system remains superconducting up to far larger currents, leading to the pronounced diodic response. Our dissipative Ginzburg-Landau simulations detail the involved processes, and provide reliable geometric and parametric ranges for the experimental realization of such a nonvolatile superconducting diode, which operates in the absence of any applied magnetic field while being fluxonic by design.

Received 21 March 2022
Revised 18 May 2022
Accepted 18 August 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.034064

Physics Subject Headings (PhySH)

Superconductivity Vortex flows Vortices in superconductors

Type-II superconductors

Time-dependent Ginzburg-Landau theory

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ji Jiang ^1,2, M.V. Milošević², Yong-Lei Wang³, Zhi-Li Xiao⁴, F.M. Peeters², and Qing-Hu Chen ^1,5,*

¹Zhejiang Province Key Laboratory of Quantum Technology and Device, School of Physics, Zhejiang University, Hangzhou 310027, China
²Department of Physics, University of Antwerp, Antwerp 2020, Belgium
³Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
⁴Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA
⁵Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China

^*qhchen@zju.edu.cn

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Vol. 18, Iss. 3 — September 2022

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Images

Figure 1
Schematic view of the superconducting film (blue) with rows of MDs (yellow) on top of it. A thin layer of insulating dioxide (gray), whose thickness is $0.5 ξ (0)$ , is coated on top of the superconductor. The size of a MD is $a = 8 ξ (0)$ in the length and $b = 5 ξ (0)$ in the width. All magnetic dots have the same thickness $1 ξ (0)$ . The magnetization direction of a MD is indicated by the red arrow, which is perpendicular to the applied current density $J$ . In the simulations, the external current is applied along $x$ direction where the periodic boundary condition is also employed. The superconductor-vacuum boundary condition is used in the $y$ direction.
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Figure 2
(a) Nucleation of VAPs driven by external currents. The background shows the distribution of the magnetic field ( $z$ component) of the MD. The shaded block indicates the geometry of the MD. The $x$ and $y$ directions indicated here are the same as those in Fig. 1, which are also shared by all the following figures concerning the superconducting film. (b) Illustration for the annihilation of VAPs. The Lorentz forces applied on the vortices and antivortices have the opposite direction (small colored arrows).
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Figure 3
Simulation results at $M = 0.17 H_{c 2}$ . (a) Current-resistance characteristics. The resistance is normalized to the resistance in the normal state $R_{N}$ and current to the GL current density $J_{GL}$ . The SDE emerges in the shaded area. Insets gives the distribution of the CPD at points $A$ and $B$ , where the applied currents are equal but in the opposite direction. The MD array is not plotted for a clean view of the CPD. (b) Distribution of supercurrent (left) and CPD (right) in equilibrium, i.e., $J = 0$ . Direction and strength of the local supercurrent is indicated by colored arrows. The MDs are denoted by shaded blocks. (c) CPDs when the external currents are $J = + 0.0069$ (left) and $- 0.0069$ (right). VAPs are pinned under the poles as shown in the left panel.
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Figure 4
(a) Evolution of the mean temperature $\bar{T}$ at the critical current $J_{c}^{+} = 0.0071$ . The red dots marked with I, II, and III represent three typical moments during superconductor-metal transition. The black curve eventually exceeds the critical temperature, indicating that a normal state can be reached finally. (b) Snapshots of CPD at the three moments I, II, and III. Image IV is the snapshot of the normal state when $t = 1500 t_{GL}$ . We use black blocks to indicate the positions of the MDs. (c) Snapshots of the corresponding temperature distribution at the four moments. (d) $I$ - $V$ characteristics of systems with intermediate heat removal (dotted) and strong heat removal (marked with crosses).
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Figure 5
(a) $I$ - $R$ characteristics at $M = 0.22 H_{c 2}$ . The shaded region now suggests the diode effect is reversed, in contrast to that of Fig. 3. The insets are visualization of CPD between two phases $J = \pm 0.0080$ , which are denoted by $A$ and $B$ , respectively. (b) Distribution of the supercurrent and the CPD in equilibrium ( $J = 0$ ). VAPs are formed due to a strong magnetization. The shaded blocks indicate the position of MD. (c) Vortex images with currents $J = + 0.0069$ (left) and $- 0.0069$ (right). The balance position of VAPs depend on the polarity of the external current.
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