Related papers: Phonon soft modes and para- to ferroelectric phase…
In this paper we elucidate the optical response resulting from the interplay of charge distribution (ionicity) and Peierls instability (dimerization) in the neutral-ionic, ferroelectric phase transition of tetrathiafulvalene-chloranil…
We analyze the ground-state properties of strongly-correlated electrons coupled with phonons by means of a generalized Gutzwiller wavefunction which includes phononic degrees of freedom. We study in detail the paramagnetic half-filled…
Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets LiYF$_4$:Ho$^{3+}$ have been measured at liquid helium temperatures in the ac and dc magnetic fields parallel to the symmetry axis of a tetragonal…
Ferropericlase (Fp), (Mg$_\mathrm{1-x}$Fe$_\mathrm{x}$)O, is the second most abundant phase in the Earths lower mantle. At relevant pressure-temperature conditions, iron in Fp undergoes a high spin (HS), S=2, to low spin (LS), S=0, state…
A potential phase transition between a normal ground state and a photon-condensed ground state in many-dipole light-matter systems is a topic of considerable controversy, exasperated by conflicting no-go and counter no-go theorems and often…
In the external field slightly inclined to the $x$- or y-axis of the frustrated tetragonal atiferromagnet Pr2CuO4, a transition is discovered from the phase with orthogonal antiferromagnetic spin subsystems along [1,0,0] and [0,1,0] to the…
Combining effective Hamiltonian and direct $ab$ $initio$ computation, we obtain the phase diagram of SnTiO$_{3}$ with respect to epitaxial strain and temperature, demonstrating the complex features of the phase diagram and providing insight…
We study a Su-Schrieffer-Heeger electron-phonon model on a square lattice by means of auxiliary-field quantum Monte Carlo simulations. The addition of a symmetry-allowed interaction permits analytical integration over the phonons at the…
We study a one-dimensional antiferromagnetic-elastic model with magnetic ions having spin $S=3/2$. By extensive DMRG computations and complementary analytical methods, we uncover a first-order transition from a homogeneous or…
The ferroelectric property of BaTiO$_3$ crystal arises from the strong Pseudo Jahn-Teller (PJT) interactions between the non-degenerate ground electronic state, $^1A_{1g}$ and the degenerate $^1T_{1u}$ symmetry states through the nuclear…
We report on optical spectroscopy on the lacunar spinels GaV$_4$S$_8$ and GeV$_4$S$_8$ in the spectral range from 100 to 23000 cm$^{-1}$ and for temperatures from 5 to 300 K. These multiferroic spinel systems reveal Jahn-Teller driven…
We present an ab initio study of the BFCO solid solution formed by multiferroics BiFeO3 (BFO) and BiCoO3 (BCO). We find that BFCO presents a strongly discontinuous morphotropic transition between BFO-like and BCO-like ferroelectric phases.…
Motivated by the recently synthesized cubic phase BaRuO$_{3}$ under high pressure and high temperature, a thorough study has been conducted on its temperature-dependent electronic properties by using the state-of-the-art \textit{ab inito}…
Investigating the competition between ferroelectric ordering and quantum fluctuations is essential to tailor the desired functionalities of mixed ferroelectric and incipient ferroelectric systems, like, (Ba,Sr)TiO3 and (Eu,Ba)TiO3.…
Low temperature properties of BaZrO3 are revealed by combining experimental techniques (X-ray diffraction, neutron scattering and dielectric measurements) with theoretical first-principles-based methods (total energy and linear response…
We discuss the first infrared reflectivity measurement on a BiFeO3 single crystal between 5 K and room temperature. The 9 predicted ab-plane E phonon modes are fully and unambiguously determined. The frequencies of the 4 A1 c-axis phonons…
In the paper, the description of the dielectric and ferroelectric properties of BaTiO_3 single crystals using Landau thermodynamic potential is addressed. Our results suggest that when using the sixth-power free energy expansion of the…
[Fe(phen)2(NCS)2] is a prototype transition metal complex material, which undergoes a phase transition between low-spin (LS) and high-spin (HS) phases, induced by temperature, pressure or light. Vibrational modes play a key role for…
Neutron inelastic scattering measurements of the polar TO phonon mode dispersion in the cubic relaxor Pb(Zn_1/3Nb_2/3)_0.92Ti_0.08O_3 at 500K reveal anomalous behavior in which the optic branch appears to drop precipitously into the…
The interplay between different degrees of freedom such as charge, spin, orbital, and lattice has received a great deal of interest due to its potential to engineer materials properties and their functionalities for device applications. In…