Picture a fisherman hauling in his nets on a calm morning at sea, when his smartwatch suddenly vibrates with an alert: “Magnetic anomaly detected – possible submarine passing 500 metres below.”Far‑fetched as it sounds, Chinese scientists have just taken a decisive step towards making that scenario real.A team from the Hefei Institutes of Physical Science and the Ningbo Institute of Materials Technology and Engineering, both under the Chinese Academy of Sciences (CAS), has created a Hall‑effect...