Gate-tunable anisotropic Josephson diode effect in topological Dirac semimetal Cd$_3$As$_2$ nanowires

Abstract

The intrinsic Josephson diode effect (JDE) has recently attracted considerable attention due to its sensitivity to broken symmetries in Josephson junctions, offering a powerful probe for uncovering hidden symmetry-breaking mechanisms in materials. The presence of higher-harmonic components in the current-phase relation, together with spin-orbital coupling, makes topological materials ideal platforms to explore this effect. In this work, we present a systematic study of the JDE in type-I topological Dirac semimetal Cd$_3$As$_2$ nanowire-based Josephson junctions. We observe a pronounced gate-tunable and highly anisotropic diode response under different magnetic-field orientations. By developing a comprehensive phenomenological model, we capture the angular dependence of the diode effect and, through temperature-dependent measurements, disentangle the respective contributions from bulk and topological surface states. Notably, anomalies in the temperature dependence of the diode efficiency reveal the coexistence of multiple transport channels, highlighting the Josephson diode effect as a sensitive probe of hidden topological superconducting states.

Figures (5)

• Figure 1: Josephson diode effect in Cd$_3$As$_2$ (device A: L=800 nm).a, Schematic of an Nb–Cd$_3$As$_2$ nanowire–Nb Josephson junction. Magnetic field orientations are defined as in-plane perpendicular ($B_{\perp}^{in}$), in-plane parallel ($B_{\!/\!/}$), and out-of-plane ($B_{\perp}^{out}$); the angle $\theta$ is measured relative to $B_{\perp}^{in}$. b, $I_b$–$V$ characteristics of up- and down-sweeps (starting from 0) at $V_g = 10 \mathrm{V}$ and $B_{\perp}^{in} = 10~\mathrm{mT}$, showing pronounced nonreciprocal switching currents $I_c^+$ and $I_c^-$. Blue dotted curve: down-sweep data plotted in absolute value. c, Dependence of $I_c^+$ and $\lvert I_c^- \rvert$ on $B_{\perp}^{in}$ at $V_g = 10~\mathrm{V}$. d, Rectification effect at selected values of $B_{\perp}^{in}$.
• Figure 2: Gate dependence of the JDE (device A: L=800 nm). (a) Differential resistance $dV/dI$ as a function of gate voltage $V_g$ and bias current $I_b$. The dark blue region corresponds to the superconducting state, which can be continuously tuned and eventually depleted by the gate. The orange curve on the right axis shows the normal-state resistance as a function of $V_g$. (b,c) Dependence of $\Delta I_c$ on the in-plane perpendicular magnetic field ($B_{\perp}^{in}$) at two representative gate voltages (3 V and 10 V). Blue and red arrows mark the minima and maxima of $\Delta I_c$, respectively. (d) Colormap of $\Delta I_c$ as a function of $V_g$ and $B_{\perp}^{in}$. Cyan and purple markers indicate the positions of the $\Delta I_c$ maxima and minima in $B_{\perp}^{in}$ as a function of $V_g$. (e,f) Gate dependence of $\Delta I_c$ and of the Q-factor.
• Figure 3: In-plane angle dependence of the JDE (device B: L=600 nm). (a)$\Delta I_c$ as a function of $B_{\perp}^{in}$ (black) and $B_{\!/\!/}$ (red). (b) Angle corresponding to the maximum $\Delta I_c$ plotted against magnetic field strength $B_r$, comparing experimental data and theoretical calculations. (c–g) Experimental measurements of $\Delta I_c$ versus angle $\theta$ for different magnetic field strengths: $B_r = 10$, 15, 20, 30, and 35 mT. The butterfly-shaped pattern of $\Delta I_c$ in polar coordinates becomes progressively compressed as $B_r$ increases. (h–l) Calculated angular dependence of $\Delta I_c$ for the same set of magnetic field strengths.
• Figure 4: Angle dependence of the JDE in the plane normal to the wire (device C: L=500 nm).(a) Magnetic-field dependence of the critical supercurrent $I_c$ at $V_g = 10\;\mathrm{V}$. The value of $I_c$ decreases under both in-plane perpendicular field $B_{\perp}^{in}$ (red) and out-of-plane perpendicular field $B_{\perp}^{out}$ (blue). (b,c)$\Delta I_c$ and the $Q$-factor as functions of magnetic field strength. (d) Angular dependence of $I_c^{+}$ and $I_c^{-}$ at selected magnetic field strength ($B_r=$ 10 mT). (e)Angular dependence of $\Delta I_c$ at selected magnetic field strength ($B_r=$ 10 mT). (f) Calculated angular dependence of $\Delta I_c$ at selected magnetic field strength ($B_r=$ 10 mT), using the results from (b).
• Figure 5: Temperature and length dependence of the JDE (device B: L=600 nm).(a) Temperature dependence of $I_c$ at $V_g = 10~\mathrm{V}$. The measured $I_c$ (black dots) decreases monotonically with increasing temperature. Two-channel Eilenberger fits are shown as solid lines for the surface contribution (red), bulk contribution (blue), and the total supercurrent (green). (b) Temperature dependence of $\Delta I_c$ corresponding to the maximal (red) and minimal (blue) values under positive and negative magnetic fields, respectively. (c) Temperature dependence of the $Q$-factor, revealing a pronounced enhancement near $1.3~\mathrm{K}$. (d) Gate dependence of the maximal $Q$-factor for junction lengths of 500, 600, and 800 nm.