Light-Controlled Superconducting Diode Effect

• Light-Controlled Superconducting Diode Effect is a phenomenon where optical driving induces nonreciprocal superconducting transport by breaking inversion and time-reversal symmetry, achieving perfect diode states and ~54% efficiency in distinct setups.
• The approach utilizes time-dependent Ginzburg–Landau and Floquet formulations to model how monochromatic and multi-frequency lights selectively suppress one critical current, leading to directional control of supercurrent.
• The research highlights experimental implementations in nanowires, Josephson junctions, and SQUIDs by detailing drive parameters, material constraints, and coherent-light control strategies for practical superconducting devices.

Searching arXiv for papers on light-controlled/light-driven superconducting diode effects and related superconducting transport. Searching for "light-driven superconducting diode effect" and "superconducting diode light control" on arXiv. The light-controlled superconducting diode effect denotes nonreciprocal superconducting transport whose directionality is created, tuned, or optimized by optical driving. In the current arXiv literature, two closely related realizations are especially prominent: an intrinsic nonequilibrium superconducting diode effect (SDE) in which monochromatic or multi-frequency light reshapes the dc supercurrent of a driven superconductor and can produce a perfect diode with $100\%$ efficiency (Ichikawa et al., 24 May 2026), and a device-level Josephson diode effect in which coherent light controls the phase and magnitude of a Josephson current through a driven quantum dot and, when two such junctions are combined into a loop, yields a light-controlled SQUID with optimized nonreciprocal efficiency up to $\approx 54\%$ (Qiao et al., 2023). Both approaches treat light not merely as a probe but as a control parameter for superconducting rectification.

1. Diode efficiency and the meaning of “perfect” nonreciprocity

In a superconductor carrying a dc current, the forward and reverse critical currents can be defined from the time-averaged supercurrent $j_{\mathrm{dc}}(q)$ as

$$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$

The corresponding diode efficiency is

$\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$

with $-1 \le \eta \le +1$. By construction, $\eta=0$ is reciprocal, $\eta\neq 0$ is nonreciprocal, and $|\eta|=1$ is the perfect diode limit in which supercurrent flows in one direction only (Ichikawa et al., 24 May 2026).

Under irradiation, the dc supercurrent is decomposed as

$$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$

where $\approx 54\%$0 is the equilibrium current cut off wherever superconductivity is fully suppressed by light. As the ac-field amplitude $\approx 54\%$1 increases, the photo-induced contribution can drive one critical branch to zero while the opposite branch remains finite. At the threshold where, for example, $\approx 54\%$2 but $\approx 54\%$3 remains finite, $\approx 54\%$4. Numerically, the perfect SDE occurs just before the complete suppression of superconductivity (Ichikawa et al., 24 May 2026).

In the light-controlled SQUID formulation, the forward and reverse critical currents are instead extracted from the current-phase relation,

$\approx 54\%$5

and the same asymmetry measure is used,

$\approx 54\%$6

Within that device geometry, numerical optimization yields $\approx 54\%$7 up to $\approx 54\%$8 for realistic parameters (Qiao et al., 2023).

2. Symmetry constraints and dynamical symmetry breaking by light

Intrinsic SDE requires breaking both inversion $\approx 54\%$9 and time-reversal $j_{\mathrm{dc}}(q)$0. In the Ginzburg–Landau description, this appears through odd-in-$j_{\mathrm{dc}}(q)$1 terms in the expansion of the coefficients,

$j_{\mathrm{dc}}(q)$2

with $j_{\mathrm{dc}}(q)$3 only if $j_{\mathrm{dc}}(q)$4 and $j_{\mathrm{dc}}(q)$5 are broken (Ichikawa et al., 24 May 2026).

For monochromatic light with frequency $j_{\mathrm{dc}}(q)$6 and vector potential

$j_{\mathrm{dc}}(q)$7

applied along the current axis, the optical field enters through minimal coupling $j_{\mathrm{dc}}(q)$8. In a noncentrosymmetric superconductor, the even-order optical responses $j_{\mathrm{dc}}(q)$9 are in general nonreciprocal in $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$0, and therefore $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$1. Increasing $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$2 can then suppress one directional critical current before the other and produce $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$3 (Ichikawa et al., 24 May 2026).

The centrosymmetric case is qualitatively different. If $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$4, monochromatic driving preserves the combined dynamical symmetry

$$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$5

which enforces

$$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$6

and therefore $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$7. Thus monochromatic light does not by itself generate intrinsic diode behavior in a centrosymmetric superconductor (Ichikawa et al., 24 May 2026).

Two- or multi-frequency driving changes that conclusion. For

$$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$8

the symmetry $$I_{\mathrm{pls}} \equiv I_c^+ = \max\{j_{\mathrm{dc}}(q)\}, \qquad I_{\mathrm{neg}} \equiv I_c^- = -\min\{j_{\mathrm{dc}}(q)\}.$$9 is generally broken if the ratio of frequencies is not a ratio of two odd integers. Then odd-order optical responses $\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$0 contribute a dc component $\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$1 that is even in $\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$2. Even in a $\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$3-symmetric system one then obtains

$\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$4

and ultimately $\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$5 (Ichikawa et al., 24 May 2026).

3. Time-dependent Ginzburg–Landau and Floquet-type formulation

The intrinsic light-driven perfect SDE is formulated in a time-dependent Ginzburg–Landau (TDGL) framework close to $\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$6. The order parameter is taken in a single-$\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$7 form,

$\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$8

and obeys

$\eta = \frac{|I_c^+|-|I_c^-|}{|I_c^+|+|I_c^-|},$9

The instantaneous free-energy density is

$-1 \le \eta \le +1$0

so that the supercurrent is

$-1 \le \eta \le +1$1

(Ichikawa et al., 24 May 2026).

Under periodic driving, the long-time state is taken to be $-1 \le \eta \le +1$2-periodic, and the current is expanded as

$-1 \le \eta \le +1$3

A useful effective quadratic coefficient is the time average

$-1 \le \eta \le +1$4

and superconductivity is suppressed wherever $-1 \le \eta \le +1$5 (Ichikawa et al., 24 May 2026).

The formal solution is obtained from a Bernoulli-type integral form in the long-time limit, after which $-1 \le \eta \le +1$6 approaches a periodic function and $-1 \le \eta \le +1$7 is extracted by time averaging. In this formulation, nonlinear optical corrections enter systematically through the expansion of $-1 \le \eta \le +1$8. The central physical outcome is that photo-induced terms can selectively extinguish one critical-current branch before superconductivity is globally destroyed (Ichikawa et al., 24 May 2026).

4. Coherent-light control of Josephson transport and SQUID diode behavior

A distinct light-controlled mechanism is realized in a Josephson structure composed of two $-1 \le \eta \le +1$9-wave superconducting leads coupled through a two-level quantum dot driven by coherent light. The total Hamiltonian is

$\eta=0$0

where $\eta=0$1 and $\eta=0$2 are BCS lead Hamiltonians, $\eta=0$3 is the bare two-level dot, $\eta=0$4 is the tunneling term, and the coherent drive is

$\eta=0$5

Here $\eta=0$6, $\eta=0$7 is the detuning, and $\eta=0$8 is the optical phase (Qiao et al., 2023).

After transforming to a rotating frame,

$\eta=0$9

and imposing $\eta\neq 0$0, the Hamiltonian becomes time-independent in the new frame. The effect of the optical phase is then explicit: $\eta\neq 0$1 Integrating out the leads gives a dc Josephson-like relation

$\eta\neq 0$2

Both the phase $\eta\neq 0$3 and the critical current $\eta\neq 0$4 are therefore controlled by the phase, intensity, and detuning of the driving light (Qiao et al., 2023).

In the weak-coupling limit $\eta\neq 0$5, the critical current exhibits a Fano-type dependence on drive amplitude through the dressed levels

$\eta\neq 0$6

As $\eta\neq 0$7 increases, the resonances at $\eta\neq 0$8 generate a positive peak, a zero crossing, and a negative peak in $\eta\neq 0$9, corresponding to a phase reversal or $|\eta|=1$0-junction behavior (Qiao et al., 2023).

When two such light-driven junctions are embedded in a superconducting loop, each with optical phase $|\eta|=1$1, the junction currents become

$|\eta|=1$2

and the total SQUID current is

$|\eta|=1$3

with $|\eta|=1$4. If $|\eta|=1$5, this reduces to the interference form

$|\eta|=1$6

If $|\eta|=1$7 or $|\eta|=1$8, the current-phase relation becomes asymmetric, $|\eta|=1$9, and the forward and reverse critical currents differ, producing a Josephson diode effect. Numerical optimization gives $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$0 up to $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$1 for realistic parameters such as $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$2, $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$3, and $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$4 (Qiao et al., 2023).

5. Material constraints, drive parameters, and experimental signatures

For the intrinsic perfect SDE, the light frequency must be below or on the order of the superconducting gap, $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$5, so that the TDGL description remains valid and quasiparticle heating is minimized. Representative estimates are given for two regimes: a low-$$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$6 metal with $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$7 and $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$8, for which $$j_{\mathrm{dc}}(q)=j_{\mathrm{eq}}'(q)+j_{\mathrm{photo}}(q),$$9 and $\approx 54\%$00 can reach perfect SDE; and a high-$\approx 54\%$01 cuprate with $\approx 54\%$02 and $\approx 54\%$03, for which $\approx 54\%$04 and $\approx 54\%$05 are quoted (Ichikawa et al., 24 May 2026).

Microscopically, strong antisymmetric spin–orbit coupling or a finite magnetic field $\approx 54\%$06 is needed to generate a nonzero $\approx 54\%$07 of order $\approx 54\%$08–$\approx 54\%$09. In Rashba–Zeeman models, $\approx 54\%$10 gives $\approx 54\%$11 if $\approx 54\%$12. Heavy-fermion materials with small $\approx 54\%$13 or intrinsically noncentrosymmetric superconductors can reduce this field. The optical polarization must be linear and aligned along the current-flow direction, so that $\approx 54\%$14, and continuous-wave irradiation is assumed, with heating managed for example on micro- or nano-structured samples or with heat sinks (Ichikawa et al., 24 May 2026).

The proposed intrinsic experimental geometry is a narrow superconducting wire or Josephson junction with known inversion breaking, including examples such as Nb/V/Ta superlattice, Rashba 2DEG, $\approx 54\%$15-BiTeI, and Kagome $\approx 54\%$16. A continuous-wave microwave or THz beam polarized along the wire is applied, and the $\approx 54\%$17-$\approx 54\%$18 characteristic is measured in forward and reverse directions as a function of light intensity and frequency. The perfect SDE is signaled by one branch of the differential resistance showing zero critical current, meaning an immediate transition to the resistive state at infinitesimal bias, while the opposite branch still carries a finite zero-resistance supercurrent. Additional probes include harmonic mixing through $\approx 54\%$19 or $\approx 54\%$20 polarized voltage and pump–probe spectroscopy of the Higgs amplitude mode through second-harmonic generation or inverse Faraday effect (Ichikawa et al., 24 May 2026).

For the quantum-dot Josephson platform, representative experimental scales are an Al-based gap $\approx 54\%$21 ($\approx 54\%$22) and dot–lead coupling $\approx 54\%$23 ($\approx 54\%$24). The drive frequency is in the few-GHz to tens-GHz range so that $\approx 54\%$25, and Rabi amplitudes $\approx 54\%$26 are stated to be reachable with on-chip microwave lines or circuit-QED resonators. Candidate platforms include gate-defined InAs or InSb nanowire quantum dots with Al contacts, self-assembled SiGe quantum dots, carbon-nanotube Josephson transistors, and circuit-QED artificial atoms in the strong-drive regime. Measurement proceeds by embedding the device in a SQUID loop and performing dc current–voltage sweeps to extract $\approx 54\%$27, optionally using a weak magnetic flux or a reference junction for phase calibration, or by RF reflectometry of microwave resonators coupled to the diode junction to detect nonreciprocal admittance (Qiao et al., 2023).

6. Conceptual distinctions, recurring misconceptions, and research significance

A useful distinction is between two analytically different forms of light-controlled superconducting rectification:

Aspect	Intrinsic driven superconductor	Light-driven Josephson device
Control principle	Photo-induced modification of $\approx 54\%$28 through $\approx 54\%$29	Optical control of $\approx 54\%$30 and of $\approx 54\%$31
Symmetry route	$\approx 54\%$32 and $\approx 54\%$33 breaking, or dynamical-symmetry breaking by multi-frequency light	Asymmetric interference in a two-junction SQUID with $\approx 54\%$34 or $\approx 54\%$35
Reported efficiency	Perfect SDE with $\approx 54\%$36	Optimized $\approx 54\%$37

This comparison suggests that “light-controlled superconducting diode effect” is not a single mechanism but a family of optically tuned nonreciprocal phenomena spanning bulk nonequilibrium transport and circuit-level Josephson interference (Ichikawa et al., 24 May 2026, Qiao et al., 2023).

Several misunderstandings are directly excluded by the cited formulations. First, monochromatic irradiation does not generically produce a diode effect in any superconductor: in a centrosymmetric system, the dynamical symmetry $\approx 54\%$38 forces $\approx 54\%$39 and therefore $\approx 54\%$40. Multi-frequency driving is essential there because it breaks the relevant dynamical symmetry and activates odd-order optical responses (Ichikawa et al., 24 May 2026). Second, “light-only” control does not imply identical microscopic requirements across platforms. In the intrinsic mechanism, strong antisymmetric spin–orbit coupling or a finite magnetic field may be required to generate the odd-in-$\approx 54\%$41 GL coefficient $\approx 54\%$42, whereas the coherent-light transistor and SQUID proposal states that its diode functionality is achieved with no magnetic field required (Ichikawa et al., 24 May 2026, Qiao et al., 2023). Third, the perfect intrinsic diode state is not described as a broad plateau deep inside an otherwise unchanged superconducting phase; numerically it occurs just before complete suppression of superconductivity (Ichikawa et al., 24 May 2026).

The broader significance of these results lies in symmetry engineering under nonequilibrium drive. One route uses light to reshape the GL coefficients and the dc current landscape until one critical branch vanishes; the other uses optical phase, intensity, and detuning to coherently reprogram Josephson transport, including $\approx 54\%$43-junction behavior and SQUID nonreciprocity. Taken together, the two approaches establish that optical control can act either at the level of the superconducting condensate itself or at the level of junction interference, and that both routes are compatible with experimentally specified frequency, field, and device scales (Ichikawa et al., 24 May 2026, Qiao et al., 2023).