Insulator-metal transitions and colossal magnetoresistance
in doped manganites

Govinda Venketeswara Pai

Electronic Correlation Division, Max-Planck-Institute for the Physics of Complex Systems,
Nöthnitzer Str. 38, D-01187 Dresden, Germany

Doped Manganites show a wide variety of interesting phenomena, most spectacular among them being the colossal magnetoresistance (CMR) observed near the ferromagnetic metal to paramagnetic insulator transition. We have developed an effective theory incorporating all the strong interactions in the problem, namely the Hund's coupling, the Jahn-Teller effect, and Hubbard correlations. The effective Hamiltonian arising in the strong Jahn-Teller limit is studied using the dynamical mean field theory. It gives a qualitative, and in many cases quantitative as well, account of the doping and temperature driven metal-insulator transitions, CMR, and material trends and material trends.