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Light Creates a Magnet in a Superconductor ✛ ✎

Original: "Microwave-Induced Optomagnetism in High-Temperature Superconductors"
· Anoop Dhillon, Amir Borji, Hamed Majedi
arXiv:2608.31127v1 · 2026-08-31 · arXiv non-exclusive · independent analysis · 1 min
Superconductivity
Microwaves with a rotating electric field turned a superconductor into a permanent magnet.

Usually, a magnetic field is created by a coil carrying a current. But in this experiment, a magnet appeared in a superconductor when microwaves were directed at it. Light with a rotating electric field made the electrons move in circles, and since there is no resistance in a superconductor, this motion does not decay. The result is a permanent magnetic field.

To make sure the effect was not due to heating, the polarization of the light was switched 83 thousand times per second. With linear polarization, there was no signal, but with circular polarization, it appeared only below the transition temperature.

The practical benefit is that such contactless magnets could replace wires in quantum computers. Wires heat up and disturb qubits, whereas light controls the magnetic field without losses.

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The effective optomagnetic conversion of 1.75 T/(W/cm²) means that microwave radiation with a power of just 1 W per square centimeter creates a magnetic field of nearly two tesla. For comparison, a typical neodymium magnet provides about 1.2 T at its surface.

\langle \tilde{M} \rangle = \gamma(\omega) \operatorname{Im}[\tilde{E} \times \tilde{E}^*]
Magnetization is proportional to the gyration coefficient and the imaginary part of the cross product of the electric field with its complex conjugate
\gamma(\omega) = \frac{n_s e^3}{4 m_s^{*2} \omega^3} + \frac{n_n e^3}{4 m_n^{*2} \omega^3} \frac{\omega^2 \tau_n^2}{1 + \omega^2 \tau_n^2}
Contribution from the superconducting condensate and normal quasiparticles; at microwave frequencies, the normal component contribution is suppressed by a factor of 10^7
\tilde{\rho}_H = \frac{\tilde{\sigma}_{xy}}{\tilde{\sigma}_{xx}^2 + \tilde{\sigma}_{xy}^2}
Hall resistance is expressed through the gyromagnetic conductivities of both fluids
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magnetophotonic effects Faraday's law of electromagnetic induction Faraday effect light induced superconductivity magneto optical kerr effect cryogenic microwave measurement microwave signal magnetic vortex thin film superconductivity superconducting phase transition flux pinning magnetic refrigeration high temperature superconductor thermoelectric device superconducting wire optical vortex ferroelectric antiferromagnetic order Wave Function Collapse faraday constant