Quasiparticles and the structure of orbital polarons in ferromagneticLaMnO3

Abstract

We investigate the spectral functions and orbital-correlation functions relative to the position of an e g hole moving in the ferromagnetic plane of orbitally ordered LaMnO 3 . Solving this problem in a self-consistent Born approximation, we analyze a hole motion as a function of uniaxial pressure, the Jahn-Teller interaction, and the polarization of orbitals in the vicinity of the hole. We report a large redistribution of the spectral weight as compared with the free hole dispersion (t), strongly dependent on the type of the alternating orbital order. Polarization of orbitals around the hole (Δ) can lead to a very narrow quasiparticle band and to large incoherent spectral weight, indicating a confinement of holes in a lightly doped LaMnO 3 insulator. It thus strongly modifies the shape of the orbital polaron, and favors the localization of small orbital polarons in the regime of Δ > t.