Theory of electronic ferroelectricity

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...

Spectral Functions of the Falicov-Kimball Model with Electronic Ferroelectricity

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 ...

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...

First-principles theory of magnetically induced ferroelectricity in TbMnO3

We study the polarization induced via spin-orbit interaction by a magnetic cycloidal order in orthorhombic TbMnO3 using first-principle methods. The case of magnetic spiral lying in the bc plane is analyzed, in which the pure electronic contribution to the polarization is shown to be small. We focus our attention on the lattice-mediated contribution, and study it’s dependence on the Coulomb int...