Direct Dipole-dipole Interaction Research Articles

Influence of direct dipole-dipole interactions on the optical response of two-dimensional materials in strongly inhomogeneous infrared cavity fields

Influence of direct dipole-dipole interactions on the optical response of two-dimensional materials in strongly inhomogeneous infrared cavity fields

Entanglement of two dipole-couples qubits induced by a thermal field of a cavity with Kerr medium

In the present work, we investigated the dynamics of two identical superconducting qubits interacting with the mode of the quantum electromagnetic field of a microwave coplanar cavity with a Kerr medium in the presence of an effective dipole-dipole interaction of the qubits. We have found an exact solution of the quantum Liouville equation for the complete density matrix of the system under consideration for the Fock and thermal chaotic initial states of the cavityr field. The exact solution for the full density matrix was used to determine the reduced qubit density matrix and to calculate the entanglement parameter concurrence. Computer simulation of the time dependence of the concurrshowed that for certain initial states of qubits, their entanglement can be significantly increased in the presence of a Kerr medium and direct dipole-dipole interaction.

Thermal Entanglement Between a Jaynes-Cummings Atom and an Isolated Atom

We studied the entanglement of a quantum system consisting of a Jaynes-Cummings atom, thermal lossless cavity and an isolated atom. The analytical expressions of the atom-atom negativity for separable and entangled initial atomic states were obtained. The influence of a detuning between the atomic transition frequency and the field frequency and direct dipole-dipole interaction on an atom-atom entanglement is examined. We showed that for a separable initial atomic states a detuning might cause high atom-atom entanglement in the presence of the dipole-dipole interaction. We also obtained that for an entangled initial atomic state a detuning causes a stabilization of an entanglement oscillations both for model with dipole-dipole interaction and model without such interaction.

Entanglement of two dipole-coupled qubits induced by a detuned thermal field

In this paper we have investigated the dynamics of entanglement of two identical qubits non-resonantly interacting with one mode of a vacuum or a thermal electromagnetic field in lossless cavity in the presence of a direct dipole-dipole interaction. Based on the exact solution to the equation used in this analysis, the Peres-Horodecki entanglement parameter (negativity) for qubits has been found. Numerical simulation of the negativity for various model parameters has been carried out. It has been shown that the interactions of qubits with a thermal field in a cavity can lead to their entanglement. It has been established that the detuning and dipole-dipole interaction of qubits can be used to manipulate and control the amount of atomic entanglement.

Cavity quantum electrodynamics in the nonperturbative regime

We study a generic cavity-QED system where a set of (artificial) two-level dipoles is coupled to the electric field of a single-mode LC resonator. This setup is used to derive a minimal quantum mechanical model for cavity QED, which accounts for both dipole-field and direct dipole-dipole interactions. The model is applicable for arbitrary coupling strengths and allows us to extend the usual Dicke model into the non-perturbative regime of QED, where the dipole-field interaction can be associated with an effective finestructure constant of order unity. In this regime, we identify three distinct classes of normal, superradiant and subradiant vacuum states and discuss their characteristic properties and the transitions between them. Our findings reconcile many of the previous, often contradictory predictions in this field and establish a common theoretical framework to describe ultrastrong coupling phenomena in a diverse range of cavity-QED platforms.

The influence of dipole-dipole interaction on entanglement of two superconducting qubits in the framework of double Jaynes-Cummins model

In this paper we investigated the entanglement dynamics between two superconducting qubits interacting with two microwave modes of independent coplanar cavities taking into account the direct dipole-dipole interaction. The model with different qubit-field couplings and detunings is under consideration. Using the dressed-states representation technique we derived the exact solution for considered model with qubits prepared initially in entangled states and vacuum field modes. We have carried out the dependence of the atom-atom entanglement on the strength of the dipole-dipole interaction and other parameters of the considered system such as different coupling constants and detunings. The results showed that the presence of a sufficiently large dipole-dipole interaction leads to stabilization of entanglement.

Surface plasmon amplification by stimulated emission of radiation in hyperbolic metamaterials

We study theoretically and numerically spasing conditions and optical dynamics of a composite hyperbolic metamaterial interacting with gain molecules. By combining Maxwell-Bloch equations with Green's function approach, we calculate lasing frequency and threshold population inversion for various gain density in the gain layer. We demonstrate high level of enhancement for photonic density of states in spacious spectral range provided by hyperbolic metastructures. We find that direct dipole-dipole interactions between molecules in the gain layer has a negligible effect on spasing conditions. We identify a region of parameters in which spasing can occur considering these effects.

Coulomb and quenching effects in small nanoparticle-based spasers

We study numerically the effect of mode mixing and direct dipole-dipole interactions between gain molecules on spasing in a small composite nanoparticles with a metallic core and a dye-doped dielectric shell. By combining Maxwell-Bloch equations with Green's function formalism, we calculate lasing frequency and threshold population inversion for various gain densities in the shell. We find that gain coupling to nonresonant plasmon modes has a negligible effect on spasing threshold. In contrast, the direct dipole-dipole coupling, by causing random shifts of gain molecules' excitation frequencies, hinders reaching the spasing threshold in small systems. We identify a region of parameter space in which spasing can occur considering these effects.

Fundamental limitation of ultrastrong coupling between light and atoms

In a recent work of ours [Phys. Rev. Lett. 112, 073601 (2014)], we generalized the Power-Zineau-Woolley gauge to describe the electrodynamics of atoms in an arbitrary confined geometry. Here we complement the theory by proposing a tractable form of the polarization field to represent atomic material with well-defined intra-atomic potential. The direct electrostatic dipole-dipole interaction between the atoms is canceled. This theory yields a suitable framework to determine limitations on the light-matter coupling in quantum optical models with discernible atoms. We find that the superradiant criticality is at the border of covalent molecule formation and crystallization.

ChemInform Abstract: Structural Characterization of Frustrated Lewis Pairs and Their Reaction Products Using Modern Solid‐State NMR Spectroscopy Techniques

AbstractReview: [45 refs.

Intermolecular Radiationless Electronic Excitation Energy Transfer Near A Conductive Film

Based on the developed mathematical model, the radiationless electronic excitation energy transfer by surface plasmons between molecules adsorbed on a conductive film is investigated. A dependence of the rate of energy transfer on the geometrical system parameters is established. It is demonstrated that the presence of the plasmon channel increases up to two orders of magnitude the probability of energy transfer in comparison with the direct dipole-dipole interaction between the donor and acceptor spaced at the same distance in vacuum.

The influence of the dipole-dipole interaction and atomic coherence on the entanglement of two atoms with degenerate two-photon transitions

Entanglement of two artificial two-level atoms with degenerate two-photon transitions is considered in the case in which the atoms interact with the thermal single-mode field in an ideal cavity. The possibility of controlling the atomic entanglement degree in such a system due to the induction of atomic coherence and direct dipole-dipole interaction of atoms is shown.

Decoherence of nuclear spins due to dipole-dipole interactions probed by resistively detected nuclear magnetic resonance

We study decoherence of nuclear spins in a GaAs quantum well structure using resistively detected nuclear magnetic resonance. The transverse decoherence time T2 of As75 nuclei is estimated from Rabi-type coherent oscillations as well as by using spin-echo techniques. By analyzing T2 obtained by decoupling techniques, we extract the role of dipole-dipole interactions as sources of decoherence in GaAs. Under the condition that the device is tilted in an external magnetic field, we exhibit enhanced decoherence induced by the change in strength of the direct dipole-dipole interactions between first nearest-neighbor nuclei. The results agree well with simple numerical calculations.

Calculation of the zero-field splitting tensor on the basis of hybrid density functional and Hartree-Fock theory

The zero-field splitting (ZFS) (expressed in terms of the D tensor) is the leading spin-Hamiltonian parameter for systems with a ground state spin S>12. To first order in perturbation theory, the ZFS arises from the direct spin-spin dipole-dipole interaction. To second order, contributions arise from spin-orbit coupling (SOC). The latter contributions are difficult to treat since the SOC mixes states of different multiplicities. This is an aspect of dominant importance for the correct prediction of the D tensor. In this work, the theory of the D tensor is discussed from the point of view of analytic derivative theory. Starting from a general earlier perturbation treatment [F. Neese and E. I. Soloman, Inorg. Chem. 37, 6568 (1998)], straightforward response equations are derived that are readily transferred to the self-consistent field (SCF) Hartree-Fock (HF) or density functional theory (DFT) framework. The main additional effort in such calculations arises from the solution of nine sets of nonstandard coupled-perturbed SCF equations. These equations have been implemented together with the spin-orbit mean-field representation of the SOC operator and a mean-field treatment of the direct spin-spin interaction into the ORCA electronic structure program. A series of test calculations on diatomic molecules with accurately known zero-field splittings shows that the new approach corrects most of the shortcomings of previous DFT based methods and, on average, leads to predictions within 10% of the experimental values. The slope of the correlation line is essentially unity for the B3LYP and BLYP functionals compared to approximately 0.5 in previous treatments.

Energy transfer from Tm^3+:^3H_5 to Dy^3+:^6F_11/2 ^6H_9/2 in selenide glasses

The effects of Tm3+ ions on the intensity and lifetime of 1.3 µm fluorescence from Dy3+ ions in Ge25Ga5Sb5Se65 glass were investigated, and the energy-transfer mechanisms were discussed. Tm3+ codoping in Dy3+-doped selenide glasses significantly enhanced the 1.3 µm fluorescence intensity and remarkably increased corresponding lifetime through an efficient energy transfer from Tm3+:3H5 to Dy3+:6F11/26H9/2. The donor (Tm3+) excitation was transferred to the acceptor (Dy3+) by direct electric dipole-dipole interaction or migrated among donor ions by diffusion-limited regime until it came into the vicinity of an acceptor ion, where direct interaction and transfer occurred.

Atom-atom interaction in an anisotropic photonic crystal

Spontaneous emission from two two-level atoms within an anisotropic photonic crystal is investigated when direct dipole-dipole interaction is taken into account. The radiation properties of the present two atoms system are similar to that of a V-type three-level atom embedded in an anisotropic photonic crystal. The direct dipole-dipole interaction can enhance or depress the spontaneous emission depending on the relative position of the upper levels from the band edge of the photonic crystals. Owing to quantum interference and the dipole-dipole interaction, the spontaneous emission spectra are complicated non-Lorentzian shapes and depend strongly on the relative position of the upper levels from the bandgap and the initial state of the system.

Resonance intermolecular energy transfer near semiconductor nanoparticles

The problem of the resonance dipole-dipole interaction between two molecules near a spherical semiconductor nanoparticle is considered. It is shown that the presence of the nanoparticle results in the additional interaction between the molecules, which, under certain conditions, can significantly exceed the direct dipole-dipole interaction. This occurs in the case when the ground-state energy of an exciton is in a close resonance with the energies of molecular transitions. The effect of the additional interaction on the probability of intermolecular resonance energy transfer is especially important at large distances between molecules. The matrix elements of the interaction are estimated for nanoparticles of semiconductor materials CuCl and GaAs.

Atom–atom interaction in an anisotropic photonic crystal

Spontaneous emission from two two-level atoms with direct dipole–dipole interaction (DDDI) between them in an anisotropic photonic crystal is investigated. The DDDI can depress or enhance the spontaneous emission, depending on the relative position of the upper levels from the bandgap.

Self-induced transparency in a resonance medium with the dipole-dipole interaction

Propagation of a pulse of self-induced transparency in a resonance medium is discussed for the case when it is necessary to take into account the direct electric dipole-dipole interaction between atoms. An equation for the envelope of a wave packet—the sine-Gordon equation—is obtained for the case of durations short compared to ω 0 −1 (ω0 is the transition frequency). The dependence of the velocity and the amplitude of the soliton on the magnitude of the dipole-dipole interaction of atoms is examined in the adiabatic approximation.

Investigation on the possibility of polar glass phase in Pb1-x Ge x Te alloys

Inverse Möbius Transform is employed to get density of states from low temperature specific heat of a dipole system in a soft matrix. It is found that polar glass state is possible for 0.007 < x < 0.035 in Pb1-x Ge x Te alloys. It is also found that both softening of lattice and increase in Ge content enhances indirect dipole-dipole interaction via soft phonons and direct dipole-dipole interaction respectively and inhibits the formation of polar glass state.