Luis Brey | PubMed Health

PubMed2005

Solitonic phase in manganites.

Orbital order present in several transition metal compounds could give rise to topological defects. Here we argue that the topological defects in orbital ordered half doped manganites are orbital solitons that carry a charge of +/-e/2. When extra charge is added to the system an array of solitons is formed and an incommensurate solitonic phase occurs. The striking experimental asymmetry in the phase diagram as electrons or holes are added to half doped manganites is explained by the energy difference between positive and negative charged solitons. The presence of nanoscale inhomogeneities in manganites is naturally explained by the existence of solitonic phases.

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PubMed2004

Continuous charge modulated diagonal phase in manganites.

We present a novel ground state that explains the continuous charge modulated diagonal order recently observed in manganese oxides, at hole concentrations x larger than one-half. In this diagonal phase the charge is modulated with a predominant Fourier component inversely proportional to 1-x. Magnetically this state consists of antiferromagnetically coupled zigzag chains. For a wide range of physical parameters such as electron-phonon coupling, antiferromagnetic interaction between Mn ions, and on-site Coulomb repulsion, the diagonal phase is the ground state of the system. Also we find that the diagonal modulation of the electron density is only a small fraction of the average charge, a much smaller modulation than the one obtained by distributing Mn+3 and Mn+4 ions. We discuss also the spin and orbital structure properties of this new diagonal phase.

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