text: Scattering from magnetic impurities destroys the pairing of time-reversed states in these materials.
full_question: Scattering from magnetic impurities destroys the pairing of time-reversed states in these materials. The properties of these materials are not affected by disorder in the system according to Anderson's theorem. In these materials, photons have a non- zero effective mass. The Nambu-Gorkov and Bogoliubov-de Gennes Hamiltonians can be used to explain these materials, which come in s-wave, p-wave, and d-wave types. One theory of these materials predicts that heat capacity varies exponentially with the band gap divided by temperature, and that the band gap's energy equals 3.5 times Boltzmann's constant times a critical temperature. In that theory, electron-phonon interactions cause the formation of bosonic particles which condense into the ground state. The London equations and BCS theory explain these materials, which expel magnetic fields in the Meissner effect. For 10 points, name these materials which have exactly zero electrical resistance.
first_sentence: Scattering from magnetic impurities destroys the pairing of time-reversed states in these materials.
raw_answer: superconductors [or word forms]