Supercurrent Diode Efficiency Reaches Perfect in Chiral Nanotube Research
Physics researchers have demonstrated how non-reciprocal persistent currents can activate a supercurrent diode effect to achieve perfect efficiency in specific nanoscale structures, addressing a longstanding mechanical question in Josephson devices.
Ginzburg-Landau Theory Shows Magnetic Fields Induce Diode Effects
The research team, featuring investigators Joseph J. Cuozzo and François Léonard, analyzed superconducting diode properties through Ginzburg-Landau theory calculations. Their numerical solutions show that applying a magnetic field parallel to a chiral nanotube induces both a diode effect and an anomalous phase across the junction. Instead, fluxoid quantization protects a non-reciprocal persistent current capable of driving the diode behavior even when higher-order pair tunneling processes are absent.
Calculations of diode efficiency ($\eta$) against normalized magnetic flux ($\hat{\Phi}$) reveal complete suppression whenever the internal magnetic flux reaches a half-integer multiple of the flux quantum ($\Phi_0$). These oscillations follow the Little-Parks effect. While widening the nanotube radius ($R$) weakens efficiency, shrinking the radius allows the diode efficiency to approach absolute perfection. Similarly, testing variations in chiral angle ($\theta$) demonstrates $\pi$-periodicity reflecting the rotational symmetry of the Ginzburg-Landau free energy functional.
Superfluid Stiffness Anisotropy Drives Performance Gains
Varying the parameter $m_1$, which controls superfluid stiffness anisotropy to leading order, alters the resulting diode efficiency significantly under a normalized magnetic field. When $m_1$ greatly exceeds $m_0$, the superfluid stiffness becomes nearly isotropic, driving diode efficiency toward zero. Conversely, in the limit where $m_1 \lesssim m_0$, efficiency reaches perfect levels regardless of the nanotube radius. This operational regime functions effectively despite minimal contributions from higher-order momentum terms in the free energy equations.
Sandia National Laboratories managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525 supported the written work authored by J.J.C., who thanked Catalin D. Spataru, Wei Pan, and Enrico Rossi for discussions. The initial manuscript version was submitted to arXiv on April 3, 2025, and later revised through February 9, 2026, establishing the theoretical framework for utilizing persistent currents to engineer high-efficiency supercurrent diodes.
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