Electrons tunnel between two objects with this property in the Josephson effect. The ratio between the penetration depth and coherence length is used in the Ginzburg-Landau theory of this property, which characterizes materials in which electrons condense to form Cooper pairs. Objects with this property exhibit perfect diamagnetism when they expel a magnetic field in the Meissner effect. YBCO is a high-temperature material exhibiting this property, which comes in Type I 
Electrons tunnel between two objects with this property in the Josephson effect. The ratio between the penetration depth and coherence length is used in the Ginzburg-Landau theory of this property, which characterizes materials in which electrons condense to form Cooper pairs. Objects with this property exhibit perfect diamagnetism when they expel a magnetic field in the Meissner effect. YBCO is a high-temperature material exhibiting this property, which comes in Type I or Type II forms. For 10 points, name this property in which materials have no electric resistance.
Electrons tunnel between two objects with this property in the Josephson effect.
superconductivity [or superconductors]