Doping and field-induced insulator-metal transitions in half-doped manganites

Abstract

We argue that many properties of the half-doped manganites may be understood in terms of a new two-(e_g electron)-fluid description, which is energetically favorable at intermediate Jahn-Teller (JT) coupling. This emerges from a competition between canting of the core spins of Mn promoting mobile carriers and polaronic trapping of carriers by JT defects, in the presence of magnetic (CE), orbital and charge order. Using it we explain features of the doping and magnetic-field-induced insulator-metal transitions such as the electron-hole asymmetry and the smallness of the transition fields.