Magnetic fields have long been known to suppress superconductivity through two main effects: first, by aligning the electron spins (Zeeman effect) and second, by raising the kinetic energy of condensed electrons via Meissner screening currents. Remarkably, in contrast with these expectations that have stood for some fifty years, it was recently discovered that magnetic fields can enhance the critical supercurrent in Nb and MoGe wires with very small diameters (typically less than 10 nm). The anomalous enhancement reaches the maximum at the field of 2-4 Tesla and is followed by usual decrease at higher fields.
The graph shows curves representing how the critical supercurrent of nanowires changes with applied magnetic field. The increase of the critical current is clearly seen. It is followed by the usual decline at higher fields.