Biomedical subjects

S Satpathy

Publications and source records attributed to S Satpathy.

At least 19 recordsLinked to original sources

PubMed2005

Wedge-shaped potential and Airy-function electron localization in oxide superlattices.

Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies of the recently fabricated, lattice-matched perovskite titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential well for the monolayer (m = 1) structure, originating from the Coulomb potential of a two-dimensional charged La sheet. The potential in turn confines the electrons in the Airy-function-localized states. Magnetism is suppressed for the monolayer structure, while in structures with a thicker LaTiO3 part, bulk antiferromagnetism is recovered, with a narrow transition region separating the magnetic LaTiO3 and the nonmagnetic SrTiO3.

Journal Article↗

PubMed2004

Does the self-trapped magnetic polaron exist in electron-doped manganites?

We show from ab initio density-functional calculations and model studies that, in the electron-doped manganite LaxCa1-xMnO3 (x<<1), unbound electrons are introduced into the conduction band, which then trap themselves in the exchange-induced magnetic potential wells forming the self-trapped magnetic polarons (STMP). Hopping beyond the nearest neighbors drastically reduces the binding energy, while the Jahn-Teller coupling increases it somewhat, resulting in a net binding of about 100+/-20 meV. The electron is self-trapped in a seven-site ferromagnetic region, beyond which the lattice is essentially antiferromagnetic. In light of the recent experiments of Neumeier and Cohn, our results suggest that the STMP may be present in the lightly electron-doped manganites.

Journal Article↗

PubMed2002

Origin of charge-orbital order in the half-doped manganites.

The microscopic origin of the charge and orbital order in the half-doped manganites is examined from ab initio density-functional calculations and exact diagonalization studies. It is shown that the dominant mechanism responsible for the charge order is the Jahn-Teller coupling, with a lesser but significant contribution from the on-site Coulomb interaction. The band structure shows a sizable interchain coupling between the zigzag chains, leading to a considerable band dispersion normal to the chains, in sharp contrast with the zigzag chain physics.

Journal Article↗

PubMed2000

Cooperative jahn-teller coupling in the manganites

The cooperative Jahn-Teller coupling between the Mn e(g) electrons and the oxygen octahedral distortions in LaMnO3 is studied using ab initio density-functional calculations and tight-binding models. The linear and quadratic vibronic coupling parameters are calculated using density-functional methods. It is shown that the cooperative Jahn-Teller coupling, primarily due to the interoctahedral electron hopping (band structure term), leads to the ordering of the octahedral distortion and simultaneously to orbital ordering. The coupling results in a two-minima adiabatic potential surface in the solid, instead of the three-minima "Mexican-hat" surface for the isolated octahedron.

Journal Article↗

PubMed1999