Zero-temperature insulator-metal transition in doped manganites

¹ Centre for Condensed Matter Theory, Department of Physics Indian Institute of Science - Bangalore 560012, India
² The Abdus Salam International Centre for Theoretical Physics Strada Costiera 11 - 34014 Trieste, Italy
³ Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore 560064, India

Corresponding authors: venkat@ictp.trieste.it hassan@physics.iisc.ernet.in hrkrish@physics.iisc.ernet.in tvrama@physics.iisc.ernet.in

Received: 19 February 2003
Accepted: 17 September 2003

Abstract

We study the transition at from a ferromagnetic insulating to a ferromagnetic metallic phase in manganites as a function of hole doping using an effective low-energy model Hamiltonian proposed by us recently. The model incorporates the quantum nature of the dynamic Jahn-Teller (JT) phonons strongly coupled to orbitally degenerate electrons as well as strong Coulomb correlation effects, and leads naturally to the coexistence of localized (JT polaronic) and band-like electronic states. We study the insulator-metal transition as a function of doping as well as of the correlation strength U and JT gain in energy , and find, for realistic values of parameters, a ground-state phase diagram in agreement with experiments. We also discuss how several other features of manganites as well as differences in behaviour among manganites can be understood in terms of our model.