Nonvolatile electric switching of critical current in cross-bar superconducting junctions

Abstract

Superconducting (SC) diodes are key passive building blocks for future SC electronics. However, realizing their active counterparts is essential for functional logic. Here, we demonstrate deterministic nonvolatile electrical switching of the critical current ($I_\text{c}$) in overlap crossbar SC junctions. By applying a minimal perpendicular magnetic field ($H_\text{z}$), $I_\text{c}$ is modulated by a factor of four with a large switching efficiency of 60\%, achieved at a significantly reduced excitation current density of $5\times10^5$~A/cm$^2$. We also uncover anomalous behaviors: an electrically switchable critical temperature and a non-monotonic $I_\text{c}$-$H_\textit{z}$ response. These observations are interpreted in terms of unique asymmetry involving isolated vortex injection, configuration and repulsion inherent to the junction geometry. Our device provides a scalable, low-power alternative to complex SQUID-based architectures, paving the way for high-density SC integrated circuits.

Figures (4)

• Figure 1: Basis transport properties of D1.a Illustration of SDEs, exhibiting critical current asymmetry. b Illustration of switchable SC devices, showing critical current manipulation via current excitation. c Schematic illustration of SC junction made of NbSe$_2$/Au/Nb. d$T$-dependence of the resistance for D1. The inset is the optical image of the device. e d$V$/d$I$ as a function of $I_\textrm{dc}$ measured at various $T$ for D1. The dashed curves mark three transition peaks of NbSe$_2$, Nb and the junction, respectively. Scale bar, 10 $\mu$m.
• Figure 2: Electric switching characteristics in D1 and D2. a-d d$V$/d$I$ versus $I_\textrm{dc}$ with a maximum bias of 240 $\mu$A at selective $H_\textit{z}$ for D1. The inset of c exhibits d$V$/d$I$ versus $I_\textrm{dc}$ with a maximum bias of 230 $\mu$A at $H_\textit{z}=-3.5$ Oe. The red and black curves denote forward and backward bias sweeps, respectively. e-f d$V$/d$I$ maps as a function of $I_\textrm{dc}$ and $H_\textit{z}$ for D1. g Extracted $I_\text{c}^\text{J}$ as a function of $H_\text{z}$ for D1. The red and black curves denote forward and backward bias sweeps, respectively. h Summary of switching efficiency ($\eta$) across different devices. i-j d$V$/d$I$ maps as a function of $I_\textrm{dc}$ and $H_\textit{z}$ for D2. k-l$R-T$ profiles of D2 switched by current pulse ($I_\text{exc}=\pm300~\mu$A) at $H_\text{z}=\pm2.4$ Oe, respectively.
• Figure 3: (a) d$V$/d$I$ versus $I_\textrm{dc}$ curves for D1 at various $T$ and appropriate $P$ for $f$ = 6.48 GHz. (b) $V_\textrm{dc}$-$I_\textrm{dc}$ curve obtained by integrating the d$V$/d$I$-$I_\textrm{dc}$ curves at different temperatures in (a). $V_\textrm{dc}$ is normalized to the integer Shapiro step separation voltage $V_0 = hf/2e$. (c) d$V$/d$I$ as a function of normalized $V_\textrm{dc}$ at $T$ near $T_\mathrm{c}$.
• Figure 4: Nonvolatile control of the SC state in D2.a d$V$/d$I$ versus $I_\textrm{dc}$ at $H_\textit{z}=2.4$ Oe. c Switching characteristics between the superconducting and normal states monitored by d$V$/d$I$. The excitation current ($I_\textit{exc}$) is set to $\pm600~\mu$A. d,e Pulse-driven switching behavior excited by 50 $\mu$s current pulses of $\pm400~\mu$A at $H_\textit{z}=2.4$ Oe and -2.4 Oe, respectively. The probe current is set to 40 $\mu$A. Scale bar, 10 $\mu$m.