Superconducting Diode Effect due to Chiral Meissner Currents in a Hollow Superconducting Helix

TL;DR

The paper tackles nonreciprocal superconducting transport (SDE) in achiral superconductors by exploiting geometric chirality in a hollow nanohelix. It employs time-dependent Ginzburg-Landau simulations in a finite-element framework to show that field-induced screening currents combine with a transport current to produce inequivalent critical currents $j_{c+}$ and $j_{c-}$, leading to a diode efficiency $\eta=(j_{C+}-j_{C-})/(j_{C+}+j_{C-})$. There are two complementary mechanisms: chiral screening currents dominating at low fields and vortex-nucleation–driven nonreciprocity at higher fields, with the maximum $\eta$ achieved when only one polarity forms vortices. This geometry-driven SDE in mesoscopic 3D structures suggests a practical path to 3D superconducting diodes for multi-level quantum circuits, with design rules such as smaller pitch and radius enhancing performance.

Abstract

The superconducting diode effect (SDE) is a key nonreciprocal phenomenon with broad relevance for superconducting electronics. Using time-dependent Ginzburg-Landau simulations, we predict and quantify a superconducting diode effect arising solely from geometric chirality imposed to a conventional superconductor. The helical geometry and magnetic-field-induced screening currents produce inequivalent critical currents for opposite polarities. The diode efficiency reaches a maximum when one current direction first nucleates vortices, revealing a chirality-controlled crossover between screening- and vortex-dominated nonreciprocity. These results establish mesoscopic geometric chirality as a robust mechanism for supercurrent rectification in an achiral superconductor. They suggest an experimentally accessible route towards 3D superconducting diodes for multi-level integrated quantum circuits.

Figures (4)

• Figure 1: (a) Geometry of the superconducting helix and field/current configuration with polarity $\pm$ as indicated. (b) Simulated current-voltage characteristic showing non-reciprocal critical currents. (c) Spatial distribution of $|\psi|^2$ near the transition for both current polarities.
• Figure 2: The distribution of (a) the $z$ component of the screening current $j_{\mathrm{s,z}}$, (b) the magnitude of the total screening current $|j_{\mathrm{s}}|$, and (c) the magnitude of the order parameter $|\psi|^2$. (d) The distribution of the screening current along the cross-sectional area of the helix (e) $j_{\mathrm{s,z}}$ on opposing sides of the cross-section.
• Figure 3: (a) The superconducting diode effect efficiency $\eta$ as a function of field for right-handed (RH) and left-handed (LH) helices. The red color gradient indicates a crossover from abrupt SN transition to an intermediate vortex mediated state. (b,c) The simulated screening current distribution at selected fields for RH and LH helices, respectively, as well as a sketch of the screening current loops. The red/blue color coding indicates the sign of $j_{s,z}$, consistent with Figure \ref{['Fig2']}. (d,e,f) Current-voltage characteristics at selected fields for a RH helix. The coloring in (d) indicates the superconducting state (S), the mixed state (V), and the normal state (N). (g) The critical current density $j_{\rm C}$ as a function of field $B_{\rm z}$ for positive (+) and negative (-) current polarities.
• Figure 4: Superconducting diode efficiency $|\eta|$ as a function of magnetic field $B_{\mathrm z}$ for various helical geometries. The reference structure has dimensions consistent with Figure \ref{['Fig1']}a. The labeling indicates deviations from this reference structure. The inset shows the efficiency as a function of pitch $p$.