Jerusalem, 17 July, 2025 (TPS-IL) — A team of Israeli, American, and British scientists cracked a century-old mystery in physics by detecting elusive magnetic signals in ordinary metals — using nothing more than visible light, the Hebrew University of Jerusalem announced on Thursday. The findings open a new frontier for materials science, electronics, and quantum technologies.
The study, published in the peer-reviewed Nature Communications, marks the first time an optical phenomenon called the Hall effect has been observed in non-magnetic metals such as copper, gold, and aluminum.
The Hall effect — discovered in 1879 — is a phenomenon in which electric currents bend in a magnetic field. In magnetic materials such as iron, this produces a strong, measurable signal. But in non-magnetic metals, the effect is far more subtle. Scientists have long theorized that a related version involving light — the Hall effect — should exist, allowing researchers to “see” how electrons respond to magnetic fields. Yet, for over a century, this remained hidden from view.
“It was like trying to hear a whisper in a noisy room,” said Prof. Amir Capua of Hebrew University’s Institute of Electrical Engineering and Applied Physics. “Everyone believed the whisper was there, but we didn’t have a microphone sensitive enough to pick it up.”
Led by Ph.D. candidate Nadav Am Shalom and Capua, and working with collaborators at the Weizmann Institute, Pennsylvania State University, and the University of Manchester, the team developed a novel approach that brought the elusive effect into focus.
Using a refined version of the magneto-optical Kerr effect (MOKE), the researchers combined a 440-nanometer blue laser with a rapidly modulated magnetic field. This dramatically boosted the technique’s sensitivity — by orders of magnitude — allowing them to detect magnetic reflections in metals previously thought too quiet to measure. MOKE is a physical phenomenon in which the polarization or intensity of light changes when it reflects off a magnetized surface.
“You might think of metals like copper or gold as magnetically inert — they don’t stick to your fridge like iron,” Capua explained. “But under the right conditions, they do react to magnetic fields, just in extremely subtle ways. For the first time, we can now detect those reactions using visible light.”
Until now, scientists attempting to measure these effects relied on electrical probes by physically attaching tiny wires to nanometer-scale devices, a process that is difficult, slow, and disruptive. This new method, by contrast, requires no physical contact at all. A simple beam of light is enough to uncover magnetic behavior.
More surprisingly, the researchers discovered that the faint optical signals — long dismissed as background noise — carried meaningful information. This “noise” followed a distinct pattern tied to spin-orbit coupling, a quantum mechanical interaction that links how electrons move to how they spin. Understanding this behavior is crucial for developing next-generation electronics such as spintronic memory and quantum logic devices.
“It’s like discovering that static on a radio isn’t just interference — it’s a hidden message,” said Am Shalom. “By tuning our instruments just right, we’ve found a way to listen to what electrons are really saying.”
The implications are far-reaching. Not only does this method open a new, non-invasive way to study magnetic behavior in common metals, it also provides a new tool for characterizing materials at the atomic level. Engineers could use this information to build faster processors, more precise sensors, and lower-power computing systems based on quantum effects.
“This research turns a nearly 150-year-old scientific problem into a powerful new opportunity,” Capua said.
