P. W. Anderson showed that this property is robust against imperfections in “dirty” materials displaying this property. Electrons in materials displaying this property pull positive charge carriers towards them, resulting in a small (-5[1])attractive force on other electrons. Within these materials, the magnetic (15[1])field obeys a Helmholtz equation with eigenvalue equal to one over the square of the (*) London penetration depth. 1.764 (10[1])times the Boltzmann constant times the critical temperature for this phenomenon gives the energy gained by forming a Cooper pair in (10[1])the BCS theory (10[1])of this (10[1])phenomenon. (10[1])For 10 points, name this low temperature phenomenon in which a material’s DC electrical resistance drops to zero. ■END■ (10[1]0[1])