Related papers: Quadrupole Arrangements and the Ground State of So…
We study $\Gamma_3$ quadrupole orders in a face-centered cubic lattice. The $\Gamma_3$ quadrupole moments under cubic symmetry possess a unique cubic invariant in their free energy in the uniform ($q=0$) sector and the triple-q sector for…
A new class of strongly infrared active structures is identified for phase III of compressed molecular H2 by constant-pressure ab initio molecular dynamics and density-functional perturbation calculations. These are planar quadrupolar…
The systematic shifts of the transition frequencies in the molecular hydrogen ions are of relevance to ultra-high-resolution radio-frequency, microwave and optical spectroscopy of these systems, performed in ion traps. We develop the…
Using a small amount of radioactive 111Cd atoms implanted in cerium lattice to probe the hyperfine electric quadrupole interaction, we have detected a quadrupole electron charge density component in alpha-Ce, which is absent in gamma-Ce.…
The transition from order to chaos in atomic nuclei has been studied analytically and numerically using a quadrupole--quadrupole residual interaction. This interaction leads to chaotic behaviour, but the critical energy $E_C\simeq 12.6$…
Through Quantum Monte Carlo simulation, we study the biquadratic-interaction model with the SU(2) symmetry in two and three dimensions. The zero-temperature phase diagrams for the two cases are identical and exhibit an intermediate phase…
We investigate disorder-driven topological phase transitions in quantized electric quadrupole insulators. We show that chiral symmetry can protect the quantization of the quadrupole moment $q_{xy}$, such that the higher-order topological…
By performing constant-pressure variable-cell ab initio molecular dynamics simulations we find a quadrupolar orthorhombic structure, of $Pca2_1$ symmetry, for the broken symmetry phase (phase II) of solid H2 at T=0 and P =110 - 150 GPa. We…
Molecular hydrogen ions are of metrological relevance due to the possibility of precise theoretical evaluation of their spectrum and of external-field-induced shifts. In homonuclear molecular ions the electric dipole $E1$ transitions are…
The first direct experimental observation of an electric quadrupole ($\textit{E}$2) transition between bound states of an atomic negative ion has been made. The transition was observed in the negative ion of bismuth by resonant (1+1)…
The role of different continuum components in the weakly-bound nucleus $^6$He is studied by coupling unbound spd-waves of $^5$He by means of simple pairing contact-delta interaction. The results of our previous investigations in a model…
We compute the thermodynamic phase diagram of seventeen elemental metals with hexagonal close-packed (hcp), face-centered cubic (fcc), and body-centered cubic (bcc) crystal structures using finite-temperature density functional theory.…
It is observed that interstitial hydrogen nucleii on a metallic lattice are strongly coupled to their near neighbours by the unscreened electromagnetic field mediating transitions between low-lying states. It is shown that the dominant…
We study by Monte Carlo simulations the effect of quenched orientational disorder in systems of interacting classical dipoles on a square lattice. Each dipole can lie along any of two perpendicular axes that form an angle psi with the…
Information on the intrinsic deformation of the proton can be obtained by studying the electromagnetic p-->Delta+ quadrupole transition. Recent experiments have shown that the electric quadrupole (E2) strength in gamma p --> Delta+ is about…
We consider the effect of the internal nuclear quadrupole interaction on quantum tunneling in complex multi-atomic two-level systems. Two distinct regimes of strong and weak interactions are found. The regimes depend on the relationship…
Structural phase transitions are accompanied by a movement of one nucleus (or a few) in the crystallographic unit cell. If the nucleus movement is continuous, a second order phase transition without latent heat results, whereas an abrupt…
Recent experiments on trilayer transition-metal dichalcogenide heterostructures have revealed the rich behavior of dipolar excitons. Motivated by these experimental observations, we investigate the collective dynamics of planar quantum…
We determine the zero temeperature phase diagram of excitons in the symmetric transition-metal dichalcogenide tri-layer heterosctructure WSe2/MoSe2/WSe2. First principle calculations reveal two distinct types of interlayer excitonic states,…
We address some properties of the quadrupole-quadrupole ($Q \cdot Q$) interaction in nuclear studies. We first consider how to restore $SU(3)$ symmetry even though we use only coordinate and not momentum terms. Using the Hamiltonian…