Spatial inhomogeneity and strong correlation physics: a dynamical mean field study of a model Mott-insulator/band-insulator heterostructure

We use the dynamical mean field method to investigate electronic properties of heterostructures in which finite number of Mott-insulator layers are embedded in a spatially infinite band-insulator. The evolution of the correlation effects with the number of Mott insulating layers and with position in the heterostructure is determined, and the optical conductivity is computed. It is shown that the heterostructures are generally metallic, with moderately renormalized bands of quasiparticles appearing at the interface between the correlated and uncorrelated regions.Comment: 4 pages, 4 figure

Electronic reconstruction in correlated electron heterostructures

Electronic phase behavior in correlated-electron systems is a fundamental problem of condensed matter physics. We argue here that the change in the phase behavior near the surface and interface, i.e., {\em electronic reconstruction}, is the fundamental issue of the correlated-electron surface or interface science. Beyond its importance to basic science, understanding of this behavior is crucial for potential devices exploiting the novel properties of the correlated systems. % We present a general overview of the field, and then illustrate the general concepts by theoretical studies of the model heterostructures comprised of a Mott-insulator and a band-insulator, which show that spin (and orbital) orderings in thin heterostructures are generically different from the bulk and that the interface region, about three-unit-cell wide, is always metallic, demonstrating that {\em electronic reconstruction} generally occurs. % Predictions for photoemission experiments are made to show how the electronic properties change as a function of position, and the magnetic phase diagram is determined as a function of temperature, number of layers, and interaction strength. Future directions for research are also discussed.Comment: Proceedings of SPIE conference on Strongly Correlated Electron Materials: Physics and Nanoengineering, San Diego, CA, 31 July - 4 August, 200

Magnetic interaction at an interface between manganite and other transition metal oxides

A general consideration is presented for the magnetic interaction at an interface between a perovskite manganite and other transition metal oxides. The latter is specified by the electron number $n$ in the $d_{3z^2-r^2}$ level as $(d_{3z^2-r^2})^n$. Based on the molecular orbitals formed at the interface and the generalized Hund's rule, the sign of the magnetic interaction is rather uniquely determined. The exception is when the $d_{3z^2-r^2}$ orbital is stabilized in the interfacial manganite layer neighboring to a $(d_{3z^2-r^2})^1$ or $(d_{3z^2-r^2})^2$ system. In this case, the magnetic interaction is sensitive to the occupancy of the Mn $d_{3z^2-r2}$ orbital. It is also shown that the magnetic interaction between the interfacial Mn layer and the bulk region can be changed. Manganite-based heterostructures thus show a rich magnetic behavior. We also present how to generalize the argument including $t_{2g}$ orbitals.Comment: 7pages, 4 figures, 1 tabl

Critical Properties of the transition between the Haldane phase and the large-D phase of the spin-1/2 ferromagnetic-antiferromagnetic Heisenberg chain with on-site anisotropy"

We analytically study the ground-state quantum phase transition between the Haldane phase and the large-$D$ (LD) phase of the $S=1/2$ ferromagnetic-antiferromagnetic alternating Heisenberg chain with on-site anisotropy. We transform this model into a generalized version of the alternating antiferromagnetic Heisenberg model with anisotropy. In the transformed model, the competition between the transverse and longitudinal bond alternations yields the Haldane-LD transition. Using the bosonization method, we show that the critical exponents vary continuously on the Haldane-LD boundary. Our scaling relations between critical exponents very well explains the numerical results by Hida.Comment: text 12 pages (Plain TeX), LaTeX sourse files of a table and a figure on reques

Interface ordering and phase competition in a model Mott-insulator--band-insulator heterostructure

The phase diagram of model Mott-insulator--band-insulator heterostructures is studied using the semiclassical approximation to the dynamical-mean-field method as a function of thickness, coupling constant, and charge confinement. An interface-stabilized ferromagnetic phase is found, allow the study of its competition and possible coexistence with the antiferromagnetic order characteristic of the bulk Mott insulator.Comment: 5 pages, 3 figures, manuscript revised, results unchange