Related papers: Ferroelectricity in (K@C$_{60}$)$_n$
A lattice generalization of the $(b_{1u}\oplus b_{2g})\otimes b_{3u}$ pseudo-Jahn-Teller model is analyzed within mean-field theory. Ferroelectric or antiferroelectric ground states are found for sufficiently large pseudo-Jahn-Teller…
Using density functional theory the ground state structural, electronic, and magnetic properties of monatomic lithium and sodium chains with low average density are investigated. A metallic, zigzag ground state structure is predicted but,…
Using first-principles density functional theoretical analysis, we predict coexisting ferroelectric and semi-metallic states in two-dimensional monolayer of h-NbN subjected to electric field and in-plane strain ($\epsilon$). At strains…
It is well known that the Hubbard model on a line graph has a flat band and ferromagnetic ground states in a certain density range. We show that for a Hubbard model on a line graph of a planar bipartite graph the ferromagnetic ground state…
Ab-initio results for structural and electronic properties of NaCl-type FeN are presented in a framework of plane-wave and ultrasoft pseudopotentials. Competition among different magnetic ordering is examined. We find the ferromagnetic…
We re-examine the nature of the ground states of bilayer graphene at odd integer filling factors within a simplified model of nearly degenerate $n=0$ and $n=1$ Landau levels. Previous Hartree-Fock studies have found that ferroelectric…
According to a continuous medium theory, in very thin ferroelectric films with real metallic electrodes (or dead layers near the electrodes) the domain structure reduces to sinusoidal distribution of ferroelectric polarization. Such a…
Strain-regulated ferroelectric (FE) materials have long attracted significant attention due to their diverse applications. While soft-phonon theory and the (pseudo) Jahn-Teller effect have achieved considerable success in providing…
Using {\it ab initio} density functional theory and single-orbital Hubbard model calculations via the density matrix renormalization group method, we systematically studied the monolayer VOI$_2$ with a $3d^1$ electronic configuration. Our…
A simple, yet accurate solution of the electron-phonon coupling problem in C_{60} is presented. The basic idea behind it is to be found in the parametrization of the ground state electronic density of the system calculated making use of…
"Hidden phases" are metastable collective states of matter that are typically not accessible on equilibrium phase diagrams. These phases can host exotic properties in otherwise conventional materials and hence may enable novel functionality…
The interplay of light and matter gives rise to intriguing cooperative effects in quantum many-body systems. This is even true in thermal equilibrium, where the electromagnetic field can hybridize with collective modes of matter, and…
We study the free energy landscape of a minimal model for relaxor ferroelectrics. Using a variational method which includes leading correlations beyond the mean-field approximation as well as disorder averaging at the level of a simple…
We present a theory of the linear and nonlinear optical characteristics of the insulating phase of the Falicov-Kimball model within the self-consistent mean-field approximation. The Coulomb attraction between the itinerant d-electrons and…
A theory to describe the dielectric anomalies and the ferroelectric phase transition induced by oxygen isotope replacement in SrTiO$_3$ is developed. The proposed model gives consistent explanation between apparently contradictory…
Results of detailed investigations of stability of phases in substances with the small difference in the energies of the ferroelectric and the antiferroelectric types of dipole ordering are presented. It is shown that interaction of locally…
The structure and polarization of the as-yet hypothetical Ruddlesden-Popper compound Pb$_2$TiO$_4$ are investigated within density-functional theory. Zone enter phonons of the high-symmetry K$_2$NiF$_4$-type reference structure, space group…
We report the remarkably robust ferroelectric state in the multiferroic compound Mn$_{1-x}$Zn$_x$WO$_4$. The substitution of the magnetic Mn$^{2+}$ with nonmagnetic Zn$^{2+}$ reduces the magnetic exchange and provides control of the various…
Ferroelectric hafnia is being explored for next generation electronics due to its robust ferroelectricity in nanoscale samples and its compatibility with silicon. However, its ferroelectricity is not understood. Other ferroelectrics usually…
Performing an exact diagonalization of the effective spin problem, a ferromagnetic ground state of kinetic origin is shown to emerge in a system of $N$ strongly correlated electrons on a $L$-site ring ($L > N$). This phenomenon is brought…