High-Temperature Superconducting Diodes

• High-temperature superconducting diodes are devices exhibiting nonreciprocal supercurrent transport, defined by unequal forward and reverse critical currents.
• They encompass implementations such as cuprate devices, twisted junctions, and intrinsic Josephson junctions, with reported efficiencies reaching up to 60% in some configurations.
• The underlying physics leverages broken inversion and time-reversal symmetries, enabling programmable, quantized outputs and paving the way for advanced superconducting circuits.

High-temperature superconducting diodes are superconducting devices that realize direction-dependent transport at elevated temperatures, most commonly through unequal critical currents $I_c^+\neq I_c^-$ for opposite current polarities, so that one direction remains dissipationless while the other becomes resistive or is strongly suppressed. In current usage the term chiefly denotes the superconducting diode effect (SDE) or Josephson diode effect (JDE) in cuprates, intrinsic Josephson junctions, twisted junctions, and related high-$T_c$ platforms, although an older literature also used “superconducting tunnel diode” for high-$T_c$ superconductor–semiconductor tunneling devices with strongly nonlinear but bias-symmetric quasiparticle transport (Qi et al., 5 Jan 2025, Ghosh et al., 2022, Hayat et al., 2013).

1. Definitions and scope

In the modern SDE literature, nonreciprocity is operationally defined by different forward and backward critical currents. A commonly used efficiency is

$\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$

with $\eta=0$ for a reciprocal device and $|\eta|=1$ for an ideal diode. A complementary intrinsic-diode notation uses $\varepsilon=I_c^-/I_c^+$ with $I_c^+>I_c^-$, so that $\eta=(1-\varepsilon)/(1+\varepsilon)$ (Qi et al., 5 Jan 2025, Hosur, 24 Dec 2025). Within this framework, “superconducting diode” usually refers to a device that supports supercurrent more readily in one direction, while “Josephson diode” denotes the same phenomenon in a weak link or Josephson junction, where the asymmetry is encoded in the current–phase relation or switching currents (Ghosh et al., 2022).

A distinct quantum limit is realized when the diode action occurs entirely within Cooper-paired states. In the quantum superconducting diode regime, microwave irradiation produces nonreciprocal Shapiro steps, so that one current direction remains at $V=0$ while the other locks to a quantized plateau

$T_c$0

with no intervening quasiparticle branch required for rectification (Wang et al., 29 Sep 2025). By contrast, the older “superconducting tunnel diode” usage referred to planar Bi$T_c$1Sr$T_c$2CaCu$T_c$3O$T_c$4-based tunnel junctions with excess voltage and nonlinear tunneling spectra, not to nonreciprocal supercurrent transport (Hayat et al., 2013).

2. Symmetry principles and thermodynamic limits

The standard symmetry requirement for nonreciprocal superconducting transport is simultaneous breaking of inversion symmetry and time-reversal symmetry. In microscopic Josephson descriptions this appears as an asymmetric current–phase relation with higher harmonics and, in some cases, an anomalous phase shift. In the skyrmion-coupled $T_c$5-wave junction proposal, for example, the supercurrent acquires a CPR of the form

$T_c$6

with asymmetry generated by Rashba spin–orbit coupling together with a noncoplanar skyrmion texture (Singh et al., 1 Nov 2025). In bulk or junction-free high-$T_c$7 cuprates, zero-field diode behavior is correspondingly interpreted as evidence for spontaneous or internally generated time-reversal-symmetry breaking once inversion symmetry is also absent or effectively broken (Gulian et al., 26 Feb 2026).

A sharp theoretical distinction separates intrinsic equilibrium diodes from engineered dynamical or device-level diodes. For intrinsic equilibrium bulk superconductors, exact $T_c$8 is impossible without non-thermodynamic behavior, and $T_c$9 can occur only upon tuning to a critical point within the superconducting state; away from such internal instabilities, Landau theory imposes a lower bound on $T_c$0 (Hosur, 24 Dec 2025). This result constrains claims of “perfect intrinsic” high-$T_c$1 diodes. It does not, however, exclude ideal behavior in Josephson structures, driven systems, or vortex-mediated devices, where the nonreciprocity is extrinsic, nonequilibrium, or circuit-defined rather than a property of a uniform equilibrium condensate (Hosur, 24 Dec 2025).

3. Cuprate high-temperature realizations

Field-free, structurally simple cuprate diodes have now been demonstrated directly in exfoliated BSCCO flakes. In a single-flake four-terminal device, the field-free SDE persists up to $T_c$2 K, reaches $T_c$3 at $T_c$4 K with $T_c$5 and $T_c$6, and remains stable for more than $T_c$7 cycles over more than $T_c$8 hours (Qi et al., 5 Jan 2025). The reported $T_c$9 is approximately symmetric about $\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$0, unlike the antisymmetric $\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$1 expected for an ordinary field-induced diode, and the polarity can change with temperature or thermal cycling. The proposed interpretation is spontaneous breaking of both inversion and time-reversal symmetries, plausibly linked to loop-current order in the pseudogap regime (Qi et al., 5 Jan 2025).

A second line of evidence comes from cuprate microbridges near and above liquid-nitrogen temperature. Tl$\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$2Ba$\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$3CaCu$\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$4O$\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$5 microbridges exhibit a pronounced superconducting diode effect at $\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$6 K under strictly zero external field, and the nonreciprocal response remains essentially unchanged for fields up to $\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$7 Oe (Gulian et al., 26 Feb 2026). The reported behavior is consistent with recent zero-field BSCCO observations and is interpreted as evidence that time-reversal-symmetry breaking may be intrinsic to the cuprate superconducting state (Gulian et al., 26 Feb 2026).

Twisted cuprate Josephson junctions define a separate high-temperature branch of the field. In artificial Josephson junctions made from twisted BSCCO layers, the Josephson diode works up to $\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$8 K, the asymmetry appears for all twist angles studied, and the maximum asymmetry reaches $\eta=\frac{I_{c+}-|I_{c-}|}{I_{c+}+|I_{c-}|},$9 at $\eta=0$0 K under a very small perpendicular magnetic field (Ghosh et al., 2022). The proposed mechanism is vortex-based: the twisted interface acts as the weakest Josephson link, and current-direction-dependent vortex configurations shift the switching distributions and critical currents (Ghosh et al., 2022).

The most advanced cuprate realization is the quantum superconducting diode in twisted high-$\eta=0$1 cuprates. There, nonreciprocity is initiated by current training without any external magnetic field, perfect diode efficiency is achieved under microwave irradiation, and quantized Shapiro outputs persist up to $\eta=0$2 K, above liquid-nitrogen temperature (Wang et al., 29 Sep 2025). Because the rectified state is locked to quantized voltages rather than an ordinary resistive branch, the output is digitized and highly resilient against input-current fluctuations as long as the drive remains on a Shapiro plateau (Wang et al., 29 Sep 2025).

4. Intrinsic Josephson junctions and engineered high-$\eta=0$3 junctions

A scalable high-temperature route is provided by the intrinsic Josephson junctions of BSCCO. In wedge-shaped intrinsic-junction devices, strong nonreciprocity arises from broken spatial and time-reversal symmetries together with enhanced anharmonicity of the current–phase relation enabled by the atomically thin barrier. Operation is demonstrated up to $\eta=0$4 K, the highest diode efficiency occurs in single-junction devices, the maximum single-junction efficiency exceeds $\eta=0$5, and a $\eta=0$6-diode serial array is realized lithographically (Wei et al., 8 Aug 2025). The same platform also supports a programmable zero-field diode state after field initialization, attributed to trapped vortices beneath the surface intrinsic junction (Wei et al., 8 Aug 2025).

The current–phase relation in such intrinsic-junction devices is explicitly $\eta=0$7-dependent. For a stack of $\eta=0$8 junctions the effective channel CPR is written as

$\eta=0$9

so the anharmonicity is effectively diluted as $|\eta|=1$0 increases (Wei et al., 8 Aug 2025). This directly explains the experimental observation that diode efficiency decreases monotonically with junction number and is maximal in the single-junction limit (Wei et al., 8 Aug 2025).

A complementary theoretical architecture uses planar $|\eta|=1$1-wave Josephson junctions coupled to a skyrmion crystal. In that proposal, two $|\eta|=1$2-wave cuprate leads proximitize a 2DEG with Rashba spin–orbit coupling, while a noncoplanar skyrmion texture breaks inversion and time-reversal symmetries, producing a strongly asymmetric current–phase relation with an anomalous phase shift (Singh et al., 1 Nov 2025). The calculated diode efficiency reaches $|\eta|=1$3 at optimized chemical potential, Zeeman coupling, superconducting gap, and skyrmion radius, and the device is explicitly designed as a field-free, gate-tunable high-temperature Josephson diode (Singh et al., 1 Nov 2025).

5. Platform-independent and programmable routes toward high-$|\eta|=1$4 diodes

One important development is the realization that high-temperature superconducting diodes need not rely exclusively on intrinsically noncentrosymmetric materials. A conventional Josephson junction driven by a biharmonic current

$|\eta|=1$5

acquires diode behavior through broken spatio-temporal symmetry alone, with polarity and efficiency set by $|\eta|=1$6 and the drive amplitudes (Borgongino et al., 11 Apr 2025). In an Al/InAs junction this yields ideal $|\eta|=1$7 from $|\eta|=1$8 Hz to GHz frequencies, wireless polarity control with an antenna, and operation up to about $|\eta|=1$9 mK; the mechanism is explicitly described as platform-independent and compatible in principle with high-$\varepsilon=I_c^-/I_c^+$0 Josephson technologies (Borgongino et al., 11 Apr 2025).

Vortex-engineered routes are likewise portable. Numerical work on thin superconducting films under inhomogeneous magnetic fields generated by adjacent current lines shows that suitably designed field profiles can create ideal half-wave rectifiers with diode efficiencies surpassing $\varepsilon=I_c^-/I_c^+$1 (Cadorim et al., 2024). Because the analysis is framed in coupled Ginzburg–Landau and heat-diffusion equations rather than a material-specific microscopic model, it is directly relevant to high-$\varepsilon=I_c^-/I_c^+$2 films operated near $\varepsilon=I_c^-/I_c^+$3 (Cadorim et al., 2024). A closely related geometric route uses conformal arrays of nanoholes: in a conventional MoGe film, conformal-mapped antidots produce millivolt-level rectification signals three orders of magnitude larger than those of a flux-quantum diode, and the method is explicitly stated to be applicable to cuprates and iron-based superconductors for higher working temperatures and larger operational fields (Lyu et al., 2021).

Programmability has emerged as a separate design axis. In a monolithic Dayem-bridge SQUID made from Ti, gate and flux control select both the magnitude and polarity of the SDE, with $\varepsilon=I_c^-/I_c^+$4 and operation up to about $\varepsilon=I_c^-/I_c^+$5 of the film’s $\varepsilon=I_c^-/I_c^+$6; the architecture is presented as material-agnostic and therefore portable to higher-$\varepsilon=I_c^-/I_c^+$7 films (Paolucci et al., 2022). Low-$\varepsilon=I_c^-/I_c^+$8 oxide-interface and electrothermal diodes extend this logic further by allowing nanoscale editing of the diode polarity or gate-controlled hotspot programming, which suggests a route to electrically reconfigurable high-$\varepsilon=I_c^-/I_c^+$9 circuits even when the underlying high-temperature implementation is still to be realized (Wang et al., 10 Nov 2025, Li et al., 14 Apr 2026).

6. Functions, controversies, and outlook

The main circuit functions now demonstrated or proposed are half-wave and full-wave rectification, direction-selective current routing, dynamically adjustable polarity, efficient logic elements, ultra-fast switches, and quantized voltage outputs. The biharmonic-drive Josephson diode is explicitly presented as a component for superconducting digital electronics, including efficient logic gates, ultra-fast switches, and dynamic half-wave supercurrent rectifiers (Borgongino et al., 11 Apr 2025). High-$I_c^+>I_c^-$0 quantum superconducting diodes add microwave-locked, quantized Shapiro outputs and therefore a digitized transfer characteristic that is resilient against current noise (Wang et al., 29 Sep 2025). At the architectural level, superconducting diodes have been proposed as on-chip nonlinear and nonreciprocal components for power delivery, coherent control, memory, high-fidelity readout, and quantum-limited amplification in integrated circuit-QED hardware (Nadeem et al., 16 Apr 2026).

Several recurring controversies are now sharply defined. First, “field-free” does not imply the absence of time-reversal-symmetry breaking; in cuprates it may indicate spontaneous internal TRS breaking, while in trained quantum diodes it may reflect metastable flux configurations written by current pulses (Gulian et al., 26 Feb 2026, Wang et al., 29 Sep 2025). Second, perfect intrinsic diode behavior is not generic in equilibrium bulk superconductors; thermodynamic arguments require internal criticality for $I_c^+>I_c^-$1, and exact $I_c^+>I_c^-$2 is forbidden in ordinary local equilibrium systems (Hosur, 24 Dec 2025). Third, the term “high-temperature superconducting diode” spans both modern supercurrent diodes and older high-$I_c^+>I_c^-$3 tunnel diodes, and those two device classes should not be conflated: the former rectify supercurrent or Josephson transport, whereas the latter display gap-induced nonlinear quasiparticle tunneling without directional supercurrent nonreciprocity (Hayat et al., 2013).

The present landscape therefore contains three converging paths. One path uses intrinsic or nearly intrinsic high-$I_c^+>I_c^-$4 materials, especially cuprates, to obtain field-free or weak-field nonreciprocity at tens of kelvin and above (Qi et al., 5 Jan 2025, Gulian et al., 26 Feb 2026). A second path uses engineered Josephson architectures—twisted cuprates, intrinsic junctions, and microwave-driven or skyrmion-coupled junctions—to obtain larger controllability, quantization, and scalability (Ghosh et al., 2022, Wei et al., 8 Aug 2025, Singh et al., 1 Nov 2025). A third path uses platform-independent dynamical, vortex, or electrothermal asymmetry to separate the diode mechanism from the choice of superconducting material, which is particularly important for future high-$I_c^+>I_c^-$5 implementations where integration, programmability, and circuit compatibility may matter as much as absolute operating temperature (Borgongino et al., 11 Apr 2025, Cadorim et al., 2024).