This work stands apart: the closest neighbors study superconductivity, semiconductors, superfluidity, and thermal conductivity, but none have connected these to the inverse Faraday effect. Nearby, researchers already know how to switch superconductivity on with heat, mold heat pathways with light, and convert heat into electricity using films. This paper takes a first step in a different direction: it shows that microwave radiation can directly create a magnetic field inside a superconductor, without coils or current lines.
On an epitaxial YBa2Cu3O7−δ film 300 nm thick, grown on a sapphire substrate, we measured the Hall voltage while passing a DC current of 1 mA. Microwave radiation at 5 GHz was delivered through a horn antenna, and polarization was switched between left and right circular at 83 kHz. The signal was extracted using lock-in detection, which separated the effect from parasitic rectification and heating. Linearly polarized radiation with amplitude modulation was used as a control.
At 80 K, below the superconducting transition, the Hall signal grew monotonically with microwave power from −4.5 to −2 dBm. With linear polarization and upon heating to 110 K, the signal was absent. The effective optomagnetic conversion reached 1.75 T/(W/cm²), several orders of magnitude higher than optical analogs. With further power increase, the signal dropped sharply to zero when the calculated internal field exceeded the lower critical field of 0.82 μT. Then, at powers of +1 and +3 dBm, narrow peaks appeared, coinciding with the third and fourth harmonics of the vortex lattice frequency.
Unlike neighboring works, where magnetic effects were achieved by strain, heat, or light at the nanoscale, this is the first demonstration of stationary optomagnetism in a superconductor at microwave frequencies. This is not just an enhancement of a known effect but a qualitatively new regime: dissipationless condensate currents allow magnetization to accumulate continuously, rather than in ultrashort pulses. The work opens a direct path to contactless magnetic field control in quantum circuits without resistive heating.
The temperature dependence of the critical field predicts a shift of the signal suppression threshold to higher powers upon cooling. This can be tested by repeating measurements at 65 K and below. Further mapping of the non-stationary optomagnetic phase diagram using scanning magnetometry with NV centers or SQUIDs would reveal the full structure of vortex states. It may also be possible to study other high-temperature superconductors and thin-film heterostructures.
The result directly impacts the architecture of superconducting quantum circuits, where magnetic bias is currently created by inductive lines that introduce thermal load and crosstalk. Microwave control of magnetization could replace these lines and reduce qubit decoherence. Additionally, the method is suitable for spectroscopy of vortex dynamics in type-II superconductors.
Repeat measurements at several temperatures below 80 K to verify the predicted shift of the vortex entry threshold. Conduct direct observation of the induced magnetization using scanning magnetometry.
This work addresses the unresolved question of non-equilibrium electrodynamics of type-II superconductors: how external radiation shapes and orders the vortex lattice. The observed collapse and subsequent recovery of the Hall signal at vortex lattice harmonics provides a new tool for studying phase coherence and pinning in high-temperature superconductors.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
In the study, a 300 nm thick YBa2Cu3O7−δ film was used to measure the Hall voltage while a DC current of 1 mA was passed and microwave radiation at 5 GHz was delivered through a horn antenna. The polarization was switched between left and right circular at a rate of 83 kHz, and the signal was extracted via lock-in detection to separate the effect from heating and parasitic rectification. At 80 K, the Hall signal grew with power, showed no effect under linear polarization and in the normal state, and dropped sharply when the lower critical field was exceeded, followed by peaks at harmonics of the vortex lattice.
Where its strength is
This work is the first to demonstrate stationary optomagnetism in a superconductor at microwave frequencies, achieving an optomagnetic conversion of 1.75 T/(W/cm²), which is several orders of magnitude higher than optical counterparts. The use of dissipationless condensate currents allows magnetization to accumulate continuously, opening a route to contactless magnetic field control in quantum devices without resistive losses.
Where it could go next
Worth trying
Why this may matter
If the effect can be scaled and integrated into devices, it could lead to contactless magnetic elements for quantum circuits that operate without resistive heating, which is important for scalable quantum technologies.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.53, against a usual 0.64. It looks like few have drilled nearby.
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.