Anderson's theorem (superconductivity)

In the field of superconductivity, Anderson's theorem states that superconductivity in a conventional superconductor is robust with respect to (non-magnetic) disorder in the host material. It is named after P. W. Anderson, who discussed this phenomenon in 1959, briefly after BCS theory was introduced.[1]

One consequence of Anderson's theorem is that the critical temperature T_c of a conventional superconductor barely depends on material purity, or more generally on defects. This concept breaks down in the case of very strong disorder, e.g. close to a superconductor-insulator transition. Also, it does not apply to unconventional superconductors. In fact, strong suppression of T_c with increasing defect scattering, thus non-validity of Anderson's theorem, is taken as a strong indication for superconductivity being unconventional.[2]

References

1. Anderson, P. W. (1959). "Theory of dirty superconductors". J. Phys. Chem. Solids. 11 (1–2): 26–30. Bibcode:1959JPCS...11...26A. doi:10.1016/0022-3697(59)90036-8.
2. Mackenzie, A. P.; et al. (1989). "Extremely Strong Dependence of Superconductivity on Disorder in Sr₂RuO₄". Phys. Rev. Lett. 80: 161–164. doi:10.1103/PhysRevLett.80.161.