Double Exchange Alone Does Not Explain the Resistivity ofLa1−xSrxMnO3

The ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ system with $0.2\lesssim x\lesssim 0.4$ has traditionally been modeled with a “double-exchange” Hamiltonian in which it is assumed that the only relevant physics is the tendency of carrier hopping to line up neighboring spins. We present a solution of the double-exchange model, show it is incompatible with many aspects of the data, and propose that in addition to double-exchange physics a strong electron-phonon interaction arising from the Jahn-Teller splitting of the outer Mn $d$ level plays a crucial role.