Related papers: Ferroelectricity in (K@C$_{60}$)$_n$
We demonstrate how the quantum paraelectric ground state of SrTiO$_3$ can be accessed via a microscopic $ab~initio$ approach based on density functional theory. At low temperature the quantum fluctuations are strong enough to stabilize the…
We report experimental observation of the reentrant integer quantum Hall effect in graphene, appearing in the N$=$2 Landau level. Similar to high-mobility GaAs/AlGaAs heterostructures, the effect is due to a competition between…
On the basis of the transfer matrix technique an analytical method to investigate the stationary states, for an electron in one-dimensional periodic structures in an external electrical field, displaying the symmetry of the problem is…
For Sn$_2$P$_2$S$_6$ ferroelectrics, the appearance of spontaneous polarization is related to stereoactivity of tin cations and valence fluctuations of phosphorous cations. Here, the continuous phase transition and its behavior under…
We have investigated the field-induced-changes in both the magnetization and the polarization in ferromagnet/Insulator/ferroelectric (FM/I/FE) multilayer by following both the Stoner-Wohlfarth (SW) model and the Landau theory. It has been…
The crystallographic stacking order in multilayer graphene plays an important role in determining its electronic properties. It has been predicted that a rhombohedral (ABC) stacking displays a conducting surface state with flat electronic…
Nesting in a semimetal can lead to an excitonic insulator state with spontaneous coherence between conduction and valence bands and a gap for charged excitations. In this paper we present a theory of the ferromagnetic state that occurs when…
For Sn$_2$P$_2$S$_6$ ferroelectrics the second order phase transitions line is observed until reaching the tricritical point at transition temperature lowering to 250 K by compression. Observed temperature-pressure phase diagram agrees with…
In this work, the ground states of the Hubbard model on complete graph are studied, for a finite lattice size $L$ and arbitrary on-site energy $U$. We construct explicitly the ground states of the system when the number of the electrons…
In this paper, we present a microscopic model for heterogeneous ferroelectric and an order parameter for relaxor phase. We write a Landau theory based on this model and its application to ferroelectric PbFe$_{1/2}$Ta$_{1/2}$O$_3$ (PFT) and…
Phonon spectra of the paraelectric phase, structure and distribution of polarization in the polar ground state, and energies of ferroelectrically and antiferroelectrically ordered phases were calculated for stress-free…
Exact ground states of interacting electrons on the diamond Hubbard chain in a magnetic field are constructed which exhibit a wide range of properties such as flat-band ferromagnetism and correlation induced metallic, half-metallic or…
The ferroelectricity in $\mathrm{HfO}_2$ thin films is widely attributed to the formation of a polar orthorhombic phase named OIII phase. However, the complexity of OIII phase originated from its low symmetry becomes an obstacle for…
The compound Ba3HoRu2O9 magnetically orders at 50 K (TN1) followed by another complex magnetic ordering at 10.2 K (TN2). The 2nd magnetic phase transition was characterized by the co-existence of two competing magnetic ground states…
A new investigation of the coexistence and competition of ferroelectricity and superconductivity is reported. In particular we show that the starting Hamiltonian of a previous study by Birman and Weger (2001) can be exactly diagonalized.…
A brief review of theory of ferromagnetism of dilute magnetic semiconductors of the form (A,Mn)B based on the double exchange model is first given. A systematic investigation of the phenomena extending the current theory is outlined. We…
A mean-field model explaining most of the details in the magnetic phase diagram of ErNi_2B_2C is presented. The low-temperature magnetic properties are found to be dominated by the appearance of long-period commensurate structures. The…
The ferromagnetic phase diagram of the periodic Anderson model is calculated using dynamical mean-field theory in combination with the modified perturbation theory. Concentrating on the intermediate valence regime, the phase boundaries are…
We show through both theoretical arguments and numerical calculations that graphene discerns an unconventional sequence of quantized Hall conductivity, when subject to both magnetic fields (B) and strain. The latter produces time-reversal…
We show the first-principles evidence of a hitherto unreported type of ferroelectricity with ultra-long ion-displacement in sodium and potassium hydroxides. Even a small amount of proton vacancies can completely change the mode of…