According to Phys.org, researchers from Japan’s Institute of Science Tokyo have developed a theoretical method to make magnetic materials effectively violate Newton’s third law using light. The team led by Associate Professor Ryo Hanai demonstrated that irradiating magnetic metals with precisely tuned light frequencies induces non-reciprocal interactions between magnetic layers. This creates a spontaneous “chase-and-run” rotation where one magnetic layer constantly follows while the other flees, effectively breaking the action-reaction symmetry. Their findings were published in Nature Communications on September 18, 2025, and the required light intensity appears achievable with current experimental capabilities. The work bridges concepts between active matter physics and condensed matter systems.
<h2 id="how-light-breaks-physics”>How light breaks physics
Here’s the thing about Newton’s third law – for every action, there’s an equal and opposite reaction. It’s one of those fundamental rules that usually holds true in physics. But this team found a clever loophole. They’re using light to selectively open “decay channels” in magnetic metals, creating an energy imbalance between different spins. Basically, they’re hacking the system so some spins get energy while others don’t, breaking the symmetry that normally enforces reciprocal interactions.
The key is what’s called the RKKY interaction – that’s Ruderman-Kittel-Kasuya-Yosida for anyone keeping score – which normally governs how spins interact in magnetic metals. By hitting the material with just the right light frequency, they can make this normally balanced interaction become lopsided. One magnetic layer tries to align with its neighbor while the neighbor tries to anti-align. The result? They start chasing each other in circles indefinitely.
Why this matters
Now, you might be thinking – cool physics trick, but so what? Well, non-reciprocal interactions are everywhere in nature once you start looking. Your brain’s neurons interact this way. Predator-prey relationships work like this. But we haven’t been able to engineer this behavior in solid-state systems until now.
This opens up wild possibilities for controlling quantum materials with light. We’re talking about potential applications in spintronics, frequency-tunable oscillators, and even manipulating strongly correlated electron systems. The researchers think this approach could extend to Mott insulators and superconductivity too. That’s not just incremental progress – that’s potentially game-changing for how we design next-generation electronic devices.
The bigger picture
What’s really fascinating here is how they’re bridging completely different fields of physics. They’re taking concepts from active matter – the study of systems like biological tissues and swarming particles – and applying them to solid-state physics. It’s like they found a universal language for non-equilibrium behavior that works across scales.
The fact that they estimate the required light intensity is within reach of current experimental setups means we might see experimental verification relatively soon. And if this works in practice? We could be looking at a whole new toolbox for material scientists. Imagine being able to program magnetic behaviors on the fly just by shining different frequencies of light. That’s the kind of control that could lead to technologies we haven’t even imagined yet.
You can dive into the full technical details in their Nature Communications paper if you’re curious about the mathematical framework. But the big takeaway is simple: sometimes breaking the rules leads to the most interesting physics.
