Abstract
We study the spectral function of a single hole doped into the plane of the Mott insulator , with antiferromagnetic (AF) spin order of spins accompanied by alternating orbital (AO) order of active orbitals. Starting from the respective model, with spin-orbital superexchange and effective three-site hopping terms, we derive the polaron Hamiltonian and show that a hole couples simultaneously to the collective excitations of the AF/AO phase, magnons, and orbitons. Next, we solve this polaron problem using the self-consistent Born approximation and find a stable quasiparticle solution—a spin-orbital polaron. We show that the spin-orbital polaron resembles the orbital polaron found in systems, as e.g., in or (to some extent) in , and that the hole may be seen as confined in a stringlike potential. However, the spins also play a crucial role in the formation of this polaron—we explain how the orbital degrees of freedom: (i) confine the spin dynamics acting on the hole as the classical Ising spins and (ii) generate the string potential which is of the joint spin-orbital character. Finally, we discuss the impact of the results presented here on the understanding of the phase diagrams of the lightly doped cubic vanadates.
3 More- Received 28 February 2009
DOI:https://doi.org/10.1103/PhysRevB.79.224433
©2009 American Physical Society
Viewpoint
Challenging a hole to move through an ordered insulator
Published 29 June 2009
A theoretical framework to explain how a hole moves through an antiferromagnetically and orbitally ordered lattice could also provide insight into the interplay between these two ordered phases.
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