Electronic structure and ferroelectricity inSrBi2Ta2O9

Intermediate coupling theory of electronic ferroelectricity.

We calculate the quantum phase diagram of an extended Falicov-Kimball model for one- and two-dimensional systems in the intermediate coupling regime. Even though some features of the phase diagram are obtained analytically, the main results are calculated with a constrained path Monte Carlo technique. We find that this regime is dominated by a Bose-Einstein condensation of excitons with a built...

Electronic Structure and Ferroelectricity in Srbi 2 Ta 2 O 9

The electronic structure of SrBi 2 Ta 2 O 9 is investigated from first-principles, within the local density approximation, using the full-potential linearized augmented plane wave (LAPW) method. The results show that, besides the large Ta(5d)-O(2p) hybridization which is a common feature of the ferroelectric perovskites, there is an important hybridization between bismuth and oxygen states. The...

Spectroscopic Studies on Electronic Ferroelectricity in Organic Conductors

Organic conductors exhibit unusual physical properties due to the critical nature of valence electrons fluctuating under localizing and delocalizing regime. Recently, we discovered that an organic superconductor, α-(BEDT-TTF)2I3 [BEDTTTF: bis(ethylenedithio)tetrathiafulvalene], induces optical second-harmonic generation (SHG) along with charge-ordering driven by the repulsive electron-electron ...

Spectral Functions of the Falicov-Kimball Model with Electronic Ferroelectricity

Magnetically induced electronic ferroelectricity in half-doped manganites.

Using a joint approach of density functional theory and model calculations, we demonstrate that a prototypical charge ordered half-doped manganite La1/2Ca1/2MnO3 is multiferroic. The combination of a peculiar charge-orbital ordering and a tendency to form spin dimers breaks the inversion symmetry and leads to a ferroelectric ground state with a polarization up to several microC/cm2. The presenc...