Superconductivity is one of the most striking collective phenomena in quantum materials. When certain materials are cooled below a characteristic transition temperature, their electrical resistance vanishes and electric current can flow without dissipating energy as heat. This unusual behavior arises because electrons form correlated pairs, known as Cooper pairs, which move collectively through the material, like a wave. Superconductors are therefore attractive for technologies ranging from powerful magnets and sensitive detectors to quantum circuits. However, this dissipationless state has its limits: if the current becomes too large, superconductivity breaks down. The critical current is a key property of any superconductor, defining the maximum current it can carry before electrical dissipation appears.In type-II superconductors, however, this experimentally observed limit is often not determined directly by the microscopic properties of the superconducting state. Instead, it is typically governed by the motion of vortices—tiny regions through which magnetic flux penetrates the material. At sufficiently high current, the vortices start to move, generating resistance and heat that can push the material out of its superconducting state.
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