マイスナー効果
Due to the Meissner effect, the magnetic induction inside the superconductor is zero. More exactly, magnetic field penetrates into a superconductor over a small distance called London's magnetic field penetration depth (denoted and usually ). The screening currents also flow in this -layer near the surface, creating magnetization inside the superconductor, which perfectly compensates the applied field , thus resulting in inside the superconductor.