Effect Of Coulomb Interaction Research Articles

Photon-assisted destructive interference through a parallel-coupled double quantum dots

In this paper, we establish a model to realize the photon-assisted destructive interference phenomena, the model consisting of parallel-coupled double quantum dots and Luttinger liquid leads. By applying the canonical transformation and the nonequilibrium Green’s function technique, the general time-dependent current formula is developed. The joint effects of the intralead Coulomb interaction and an external ac field on the quantum interference are investigated. For weak intralead interactions, besides the usual photon-assisted tunneling resonance, there are two types of photon-assisted tunneling destructive interference: one is related to interdot coupling and the other to intralead interactions. For moderately strong intralead interaction, the photon-assisted sidebands are suppressed and the differential conductance scales as a power law in bias voltage. In particular, we show the multiphoton absorption and emission up to four photons in an electron tunneling process. We believe that the photo-assisted destructive interference results obtained in this paper are instructive for future experiments.

Topological Phase Diagram of an Interacting Kitaev Chain: Mean Field versus DMRG Study

In this work, we study the topological phase transitions of a Kitaev chain generalized by the addition of nearest-neighbor Coulomb interaction. We show the presence of a robust topological phase as a function of the interaction strength and of the on-site energy with associated non-zero energy Majorana states localized at the chain edges. We provide an effective mean-field model that allows for the self-consistent computation of the mean value of the local particle number operator, and we also perform Density Matrix Renormalization Group numerical simulations based on a tensor network approach. We find that the two methods show a good agreement in reporting the phase transition between trivial and topological superconductivity. Temperature robustness within a physically relevant threshold has also been demonstrated. These findings shed light on an entire class of topological interacting one-dimensional systems in which the effects of residual Coulomb interactions play a relevant role.

Modeling the structure of the dayside Venusian ionosphere: Impacts of protonation and Coulomb interaction

The CO$_2$-dominated thick atmosphere of Venus coexists with an ionosphere that is mainly formed, on the dayside, via the ionization of atmospheric neutrals by solar extreme ultraviolet and soft X-ray photons. Despite extensive modeling efforts that have reproduced the electron distribution reasonably well, we note two main shortcomings with respect to prior studies. The effects of protonation and Coulomb interaction are crucial to unveiling the structure and composition of the Venusian ionosphere. We evaluate the role of protonated species on the structure of the dayside Venusian ionosphere for the first time. We also evaluate the role of ion-ion Coulomb collisions, which are neglected in many existing models. Focusing on the solar minimum condition for which the effect of protonation is expected to be more prominent, we constructed a detailed one-dimensional photochemical model for the dayside Venusian ionosphere, incorporating more than 50 ion and neutral species (of which 17 are protonated species), along with the most thorough chemical network to date. We included both ion-neutral and ion-ion Coulomb collisions. Photoelectron impact processes were implemented with a two-stream kinetic model. Our model reproduces the observed electron distribution reasonably well. The model indicates that protonation tends to diverge the ionization flow into more channels via a series of proton transfer reactions along the direction of low to high proton affinities for parent neutrals. In addition, the distribution of O$_2^+$ is enhanced by protonation by a factor of nearly 2 at high altitudes, where it is efficiently produced via the reaction between O and OH$^+$. We find that Coulomb collisions influence the topside Venusian ionosphere not only directly by suppressing ion diffusion, but also indirectly by modifying ion chemistry. Two ion groups can be distinguished in terms of the effects of Coulomb collisions: one group preferentially produced at high altitudes and accumulated in the topside ionosphere, which is to be compared with another group that is preferentially produced at low altitudes and, instead, depleted in the topside ionosphere. Both protonation and Coulomb collisions have appreciable impacts on the topside Venusian ionosphere, which account for many of the significant differences in the model ion distribution between this study and early calculations.

The effect of Coulomb interaction on optical absorption of a quantum well wire

The optical absorption coefficient in GaAs/AlGaAs cylindrical parabolic quantum wire (QW) with an applied static-electric field is studied in detail. The Schrödinger equation is solved within the effective mass approximation and an analytical solution is used for the electronic structure of cylindrical QW. The main aim is to clarify the effect of the Coulomb interaction on the exciton-related optical absorption of a QW with no assumptions about the strength of the confinement. Finally, it is clearly shown that the further confinement due to Coulomb interaction in a quantum wire increases the transition energy, dipole matrix elements, and absorption peaks, and results with the blue shift. One cannot neglect the Coulomb interaction in the absorption calculations.

Charged particle scattering in harmonic traps

The trap method provides a novel way to extract phase shifts of neutral-particle scattering from bound-state calculations. It has been adopted successfully in several ab initio calculations to study neutron-nucleus scattering, where there is no long-range Coulomb interaction between the target and projectile. How to incorporate the effects of Coulomb interaction is a crucial problem in the trap method. In this Letter, we examine the robustness of the new proposed Coulomb-corrected Busch-Englert-Rzażewski-Wilkens (BERW) formula Guo (2021) [25] by taking proton-proton scattering as the test ground. While the numerical results are generally well consistent with conventional methods, a number of anomalous scattering energies are identified, where the Coulomb-corrected BERW formula gives less satisfactory results. The underlying theoretical reasons are analyzed in depth, which contributes to a more complete understanding of the applicable scope of the Coulomb-corrected BERW formula. Our study lays the key foundation for future ab initio studies of scattering processes between proton and light nuclei based on the trap method.

Nanoscale Investigations of the Electric Double Layer in Protic Ionic Liquids

A hydrogen-based energy storage system will be the backbone of a future energy grid using renewable energies. Polymer electrolyte membrane fuel cells (PEMFCs) are a key element in this energy system as they convert chemical energy stored as hydrogen into electrical energy on demand. PEMFC systems, especially for automotive application, could be significantly improved by increasing the operation temperature above 100 °C. Protic ionic liquids are promising candidates as non-aqueous protic electrolytes for next-generation high-temperature polymer electrolyte membrane fuel cells. These fuel cells have a target operation temperature of 160 °C and allowing for a more efficient water and heat management compared to conventional Nafion®-based PEMFCs, which operate at temperatures below 80 °C [1].In order to ensure a reliable and efficient operation an electrolyte with a high electrochemical performance and stability has to be selected. For this purpose, protic ionic liquids have been proposed and first fuel cell tests have shown promising results [2]. Hence, we aim on understanding the properties of this class of novel electrolytes on an atomistic level, which would allow designing suitable material combinations and predicting their properties for an efficient fuel cell operation. As ionic liquids are molten salts, which are liquid below 100 °C, their electrochemical properties differ significantly from those of aqueous solutions. Instead of a classical electric double layer, which can be described by the models provided by Helmholtz, Gouy-Chapman and Stern, the interface structure formed between the electrolyte and a charged electrode is governed by the interplay between coulomb interaction and steric effects between the (large) molecular ions [3]. In order to understand the formation of this double layer on a metallic electrode, we employ atomic force microscopy and infrared spectroscopy in combination with molecular dynamics simulations. Our results show that in the interface region between the prototype protic ionic liquid diethylmethylammonium triflate ([Dema][TfO]) and a Pt electrode, a dense layered structure consisting of alternating anion and cation layers is present, that extends several nanometres into the bulk of the electrolyte [4]. The composition and structure changes with applied potential due to a preferential attraction of anions or cations depending on the electrode charge. When water is added to the ionic liquid, the layered structure becomes distorted and water molecules appear near the electrode. Since the presence of water will also influence the relevant electrochemical processes such as the oxygen reduction reaction (ORR), the analysis of the double layer structure on an atomistic scale is necessary in order to understand the subtle interactions between the molecules in the electrolyte and to propose design routes for novel more efficient ionic liquid-based electrolytes. Wippermann, K.; Suo, Y.; Korte, C. Oxygen Reduction Reaction Kinetics on Pt in Mixtures of Proton-Conducting Ionic Liquids and Water: The Influence of Cation Acidity. J. Phys. Chem. C 2021, 125, 4423–4435, doi:10.1021/acs.jpcc.0c11374.Skorikova, G.; Rauber, D.; Aili, D.; Martin, S.; Li, Q.; Henkensmeier, D.; Hempelmann, R. Protic Ionic Liquids Immobilized in Phosphoric Acid-Doped Polybenzimidazole Matrix Enable Polymer Electrolyte Fuel Cell Operation at 200 °C. Journal of Membrane Science 2020, 608, 118188, doi:10.1016/j.memsci.2020.118188.Rodenbücher, C.; Wippermann, K.; Korte, C. Atomic Force Spectroscopy on Ionic Liquids. Applied Sciences 2019, 9, 2207, doi:10.3390/app9112207.Rodenbücher, C.; Chen, Y.; Wippermann, K.; Kowalski, P.M.; Giesen, M.; Mayer, D.; Hausen, F.; Korte, C. The Structure of the Electric Double Layer of the Protic Ionic Liquid [Dema][TfO] Analyzed by Atomic Force Spectroscopy. International Journal of Molecular Sciences 2021, 22, 12653, doi:10.3390/ijms222312653. Figure 1

A semi-exact analytical study of the phase diagram of the two dimensional extended Holstein-Hubbard model

An extended Holstein-Hubbard model is studied in two dimensions analytically for both weak and strong correlations. A series of unitary transformations followed by an averaging with a fully-generalized phonon state is performed to obtain an effective electronic Hamiltonian. For weak correlation, the Hartree-Fock approximation is employed and for strong correlation, the electronic Hamiltonian is mapped on to an effective t−J model which is solved using the Gutzwiller approximation and the Zubarev technique. The variation of the effective Coulomb interaction strength is studied for different electron-electron and electron-phonon interaction coefficients and the SDW-CDW phase diagram is plotted using the Mott-Hubbard metallicity criteria. A metallic regime is shown to exist at the SDW-CDW cross-over region and the width of the metallic phase is found to be broader than the result obtained by numerical diagonalization method. The metallic phase is also found to be wider in two dimensions than in one dimension.

Insights on the chloride adsorption stability in cement mortar under current field and sulfate attack: From experiments to molecular dynamics simulation

The destabilization together with boundary chloride ions releasing leads to the corrosion of steel bars, posing nonnegligible risks to the durability of structures. This work attempted to design the typical pore solution of underground constructions via methods of combining NaCl with Na2SO4 along with conducting a stray current continuously. The bound chloride stability of mortar under the action of electric current was systematically determined. The reaction mechanisms were tested by quantitative XRD, TG-DTG, FTIR, FESEM, and X-CT. Molecular dynamics was utilized to simulate the physical binding processes of C–S–H of Cl−/SO42- and their interaction under the actions of electric field by comparing the ions displacement trajectory, radial distribution function, and moving ability. The experimental results showed that the SO42- weakened the chemical chloride binding capacity with the Friedel's salt, portlandite, and calcium silicate decomposed to produce gypsum or ettringite. The electric field demonstrated less impact on the stabilities of chemical-bound Cl−, but promoted SO42- redistributions, causing substantial pore coarsening. The simulation revealed that the physical binding contained short-range ion Coulomb-interactions and long-range van der Waals interactions. The SO42- inhibited the binding of the C–S–H on Cl− by fact that the deposition large cluster of Na–SO4 blocked the nano-meter channels and competitive adsorption occurred at the SiOCa+ sites, while the introduction of electric field weakened the dominating effects of Coulomb-interactions and improved the ions desorption gradually. Hopefully, the transport and adsorption mechanisms of the Cl− in the cement-based materials can help guide the underground concrete with durability.

Thermoelectric enhancement of a parallel double quantum dot system connecting to Luttinger liquid leads

In this work, we study the thermoelectric properties of the parallel-coupled double quantum dot connected to Luttinger liquid (LL) leads. By applying nonequilibrium Green's function methods, the expressions of the electron current, heat currents, and transport coefficients are derived. We mainly focus on the effect of intralead Coulomb interaction and the spatial asymmetry of the system. Various causes for the enhancement of the thermoelectric efficiency are investigated. We find that Coulomb interactions in the LL not only enhance quantum interference but also considerably enhance thermoelectric effects. For moderately strong intralead interaction, the figure of merit can be considerably high and reach over 60 in the case of weakly coupled to LL leads and detuning of the energy levels, while in the case of strongly coupled to LL leads and the two aligned levels, the figure of merit approaches 8. The quantum interference induced by the Coulomb interaction yields a very high thermoelectric efficiency when the intralead interaction is very strong. These results may provide a design rule for the development of high-efficiency thermoelectric devices and facilitate optimization of device performance.

Improving Strain-localized GaSe Single Photon Emitters with Electrical Doping.

Exciton localization through nanoscale strain has been used to create highly efficient single-photon emitters (SPEs) in 2D materials. However, the strong Coulomb interactions between excitons can lead to nonradiative recombination through exciton-exciton annihilation, negatively impacting SPE performance. Here, we investigate the effect of Coulomb interactions on the brightness, single photon purity, and operating temperatures of strain-localized GaSe SPEs by using electrostatic doping. By gating GaSe to the charge neutrality point, the exciton-exciton annihilation nonradiative pathway is suppressed, leading to ∼60% improvement of emission intensity and an enhancement of the single photon purity g(2)(0) from 0.55 to 0.28. The operating temperature also increased from 4.5 K to 85 K consequently. This research provides insight into many-body interactions in excitons confined by nanoscale strain and lays the groundwork for the optimization of SPEs for optoelectronics and quantum photonics.

Electron-Correlation-Induced Charge Density Wave in FeGe

As the first magnetic kagome material to exhibit the charge density wave (CDW) order, FeGe has attracted much attention in recent research. Similar to AV3Sb5 (A = K, Cs, Rb), FeGe exhibits the CDW pattern with an in-plane 2×2 structure and the existence of van Hove singularities near the Fermi level. However, sharply different from AV3Sb5 which has phonon instability at M point, all the theoretically calculated phonon frequencies in FeGe remain positive. Based on first-principles calculations, we surprisingly find that the maximum of nesting function is at K point instead of M point. Two Fermi pockets with Fe-dxz and Fe-d x 2–y 2 /dxy orbital characters have large contribution to the Fermi nesting, which evolve significantly with kz , indicating the highly three-dimensional (3D) feature of FeGe in contrast to AV3Sb5. Considering the effect of local Coulomb interaction, we reveal that the instability at K point is significantly suppressed due to the sublattice interference mechanism. Meanwhile, the wave functions nested by vector M have many ingredients located at the same Fe site, thus the instability at M point is enhanced. This indicates that the electron correlation, rather than electron-phonon interaction, plays a key role in the CDW transition at M point.

Combined Effects of Intense THz Laser Field and Applied Electric Field on Binding Energy of Exciton in GaAs/GaAlAs Finite Spherical Quantum Dot

This paper describes the combined effects of intense THz laser field and electric field on the ground state binding energy of heavy hole excitons confined in GaAs/ GaAlAs spherical finite quantum dots. The formulation is based on the model of “laser dressed potential” which combines Coulomb interaction and field effect in only one potential as reported in the literature. The calculation is performed by using the variational method in the framework of the single band effective mass theory. Our results show that (i) the laser field increases the electron and hole confinement energy that form the exciton in the QD until they reach a maximum, then they become almost constant for an intense laser field, (ii)the electric field and the laser field lowers the binding energy for all quantum dot radii making the exciton stabilized and clustered near the center of the dot, and iii)the laser field increases the spatial extension of exciton but the electric field decreases it linearly.

Effects of the two-dimensional Coulomb interaction in both Fermi velocity and energy gap for Dirac-like electrons at finite temperature

Effects of the two-dimensional Coulomb interaction in both Fermi velocity and energy gap for Dirac-like electrons at finite temperature

The effect of inter-dot Coulomb interaction on the charge and energy transport properties of a five-terminal system consisting of three Coulomb-coupled quantum dots

We have studied a 5-terminal system consisting of three single level quantum dots (QDs) that are in contact with their respective reservoirs. In addition to the intra-dot Coulomb interaction, the electron in the dot affected by an inter-dot Coulomb repulsion from its adjacent QD. We describe this system by an Anderson type model Hamiltonian and apply the Greens function method to study the transport properties of the system. Since we are interested in temperatures higher than the Kondo temperature, we use the equations of motion technique to calculate Green’s functions. Numerical analysis shows that there is a correlation between the transport characteristics of the lower and upper dot and we can change the conductivity of the lower dot only by varying the parameters of the upper dot and vice versa. We demonstrated that the middle dot play the role of the switch on/off of this correlation. Also, we investigated the effect of thermoelectric properties. We found that the inter-dot Coulomb interaction can improve the thermoelectric performance of the system.

Modification of topological corner excitations at the interplay of boundary geometry and Coulomb interaction

The effect of Coulomb interaction on the 2D second order topological superconductor is investigated taking into account different geometries of the boundary in the mainframe of the mean-field approximation. The spontaneous symmetry breaking, described earlier in Aksenov et al (2023 Phys. Rev. B 107 125401), is found to be robust against the boundary deformation. Meanwhile, the details of the state with spontaneously broken symmetry is found to be dependent on the specific boundary geometry. Considering different types of the boundary of the 2D system, it is demonstrated that the deviation of the electron density in the broken symmetry state is determined by the position of the zero-dimensional (second-order) excitations with nearly zero energy. The critical value of the Coulomb interaction, at which the transition occurs, is found to be determined by the energy of these excitations, which is non-zero due to overlapping of the wave-functions at different corners.

Unveiling the strong coulomb interaction effect on electronic structures and mechanical properties of C4AF

AbstractThere are works have reported the crystal structures and mechanical properties of ferrite cement (C4AF) at the atomic scale with deviation owing to the omission of the Coulomb interaction effect (Ueff) between 3d electrons of Fe in C4AF. In this work, the DFT+U method was used to evaluate its effect on their electronic structures and mechanical properties of C4AF with two different phases I2mb (C4AF‐I) and Pnma (C4AF‐P). The FeO bonds of the two phases are all weaker and display Ueff due to the presence of Fe ions. The mechanical properties of C4AF calculated using DFT+U method significantly differ from those obtained without considering Ueff, in which the former shows lower inferior mechanical properties than the latter. This work presents a comparative study the effect of Coulomb interaction to the internal electronic structures and mechanical properties, which will pave the way for designing high hydration reaction cement and high toughness materials.

Nematic Excitonic Insulator in Transition Metal Dichalcogenide Moiré Heterobilayers.

We study the effect of interelectron Coulomb interactions on the displacement field induced topological phase transition in transition metal dichalcogenide moiré heterobilayers. We find a nematic excitonic insulator phase that breaks the moiré superlattice's threefold rotational symmetry and preempts the topological phase transition in both AA and AB stacked heterobilayers when the interlayer tunneling is weak, or when the Coulomb interaction is not strongly screened. The nematicity originates from the frustration between the nontrivial spatial structure of the interlayer tunneling, which is crucial to the existence of the topological Chern band, and the interlayer coherence induced by the Coulomb interaction that favors uniformity in layer pseudospin orientations. We construct a unified effective two-band model that captures the physics near the band inversion and applies to both AA and AB stacked heterobilayers. Within the two-band model the competition between the nematic excitonic insulator phase and the Chern insulator phase can be understood as the switching of the energetic order between the s-wave and the p-wave excitons upon increasing the interlayer tunneling.

Coulomb Corrections for Bose–Einstein Correlations from One- and Three-Dimensional Lévy-Type Source Functions

In the study of femtoscopic correlations in high-energy physics, besides Bose–Einstein correlations, one has to take final-state interactions into account. Amongst them, Coulomb interactions play a prominent role in the case of charged particles. Recent measurements have shown that in heavy-ion collisions, Bose–Einstein correlations can be best described by Lévy-type sources instead of the more common Gaussian assumption. Furthermore, three-dimensional measurements have indicated that, depending on the choice of frame, a deviation from spherical symmetry observed under the assumption of Gaussian source functions persists in the case of Lévy-type sources. To clarify such three-dimensional Lévy-type correlation measurements, it is thus important to study the effect of Coulomb interactions in the case of non-spherical Lévy sources. We calculated the Coulomb correction factor numerically in the case of such a source function for assorted kinematic domains and parameter values using the Metropolis–Hastings algorithm and compared our results with previous methods to treat Coulomb interactions in the presence of Lévy sources.

Effects of Coulomb and isospin symmetry breaking interactions on neutron-skin thickness

Both the Coulomb interaction and isospin symmetry breaking (ISB) parts of the nuclear interaction break the isospin symmetry in atomic nuclei. Effects of these two kinds of interaction on properties of atomic nuclei, especially, the mass difference of mirror nuclei and the neutron-skin thickness of $ N = Z $ and $ N \ne Z $ nuclei, are discussed. It is found that corrections to the Hartree-Fock-Slater approximation for the Coulomb interaction negligibly affect the neutron-skin thickness, while the charge-symmetry breaking term originating from the strong interaction might affect it non-negligibly. According to our calculations, the ISB terms other than the Coulomb interaction affect the estimation of the density dependence of the symmetry energy, $ L $, by about $ 0 $--$ 12 \, \mathrm{MeV} $ using the correlation with the neutron-skin thickness.

Evidence for Band Renormalizations in Strong-Coupling Superconducting Alkali-Fulleride Films.

There has been a long-standing debate about the mechanism of the unusual superconductivity in alkali-intercalated fullerides. In this Letter, using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of superconducting K_{3}C_{60} thin films. We observe a dispersive energy band crossing the Fermi level with the occupied bandwidth of about 130meV. The measured band structure shows prominent quasiparticle kinks and a replica band involving the Jahn-Teller active phonon modes, which reflects strong electron-phonon coupling in the system. The electron-phonon coupling constant is estimated to be about 1.2, which dominates the quasiparticle mass renormalization. Moreover, we observe an isotropic nodeless superconducting gap beyond the mean-field estimation (2Δ/k_{B}T_{c}≈5). Both the large electron-phonon coupling constant and large reduced superconducting gap suggest a strong-coupling superconductivity in K_{3}C_{60}, while the electronic correlation effect is suggested by the observation of a waterfall-like band dispersion and the small bandwidth compared with the effective Coulomb interaction. Our results not only directly visualize the crucial band structure but also provide important insights into the mechanism of the unusual superconductivity of fulleride compounds.