The European Physical Journal D最新文献

In this study, we investigated the electrical and thermoelectric properties of the zinc porphyrin dimer and the double-dimer zinc porphyrin molecular junctions using density functional theory (DFT) combined with the non-equilibrium Green’s function method. Our results demonstrate that the electronic transport and thermoelectric properties of these junctions can be significantly improved in the presence of another dimer. By adding a new zinc porphyrin dimer, the electrical conductance (G) increased up to an order of magnitude and showed further enhancement in the Seebeck coefficient for a good range of Fermi energies. However, the situation is the opposite in the case of the structure of zinc porphyrin dimer without any additives. These results imply that through modifications in the molecular configuration, there exists a promising potential for enhancing the figure of merit (ZT) value, thereby these systems can be potentially utilized to increase the opportunities for versus application in molecular-scale thermoelectric energy generators we conducted a comparative analysis between the zinc porphyrin dimer and the double-dimer zinc porphyrin molecular junctions.

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Zinc porphyrin dimers-based molecular wire

In recent years, there has been a growing global interest in ultra-wide bandgap semiconductor materials, with aluminium nitride emerging as a particularly promising material. Using density-functional theory (DFT) at the CAM-B3LYP/6-311G(3d,2p) basis set level, we have systematically optimized the geometries of the (AlN)₁₂ cluster. Furthermore, the structural and thermodynamic changes of these clusters under the external electric field (EEF) were investigated. When the external electric field intensity increased the energy gap decreases continuously, infrared spectral analysis showed an obvious Stark effect, and the molecular structure showed significant alterations. Additionally, the study examined orbital compositions and excitation properties of twenty excited states using time-dependent density-functional theory (TD-DFT). The results indicated a decrease in excitation energy with increasing EEF, resulting in longer wavelengths and red-shifted spectral. These findings provide an opportunity to precisely modulate the electronic properties of (AlN)₁₂ cluster by controlling the strength and direction of the EEF, opening up more possibilities for their application in photoelectronic devices.

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The conservation of the number of nodes in the wavefunctions of one-electron diatomic quasimolecules is treated. The elaborated approach is focused on the behavior of separation constants and their relationship to the number of nodes as the distance between nuclei varies. By examining the separation constants for quasimolecules with different nuclear charges, we demonstrate the robustness of the number of nodes across different states and separations without explicitly defining the wavefunctions themselves.

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A low energy particle confined by a horizontal reflective surface and gravity settles in gravitationally bound quantum states. These gravitational quantum states (GQS) were so far only observed with neutrons. However, the existence of GQS is predicted also for atoms. The GRASIAN collaboration pursues the first observation of GQS of atoms, using a cryogenic hydrogen beam. This endeavor is motivated by the higher densities, which can be expected from hydrogen compared to neutrons, the easier access, the fact that GQS were never observed with atoms and the accessibility to hypothetical short-range interactions. In addition to enabling gravitational quantum spectroscopy, such a cryogenic hydrogen beam with very low vertical velocity components—a few cm (hbox {s}^-1), can be used for precision optical and microwave spectroscopy. In this article, we report on our methods developed to reduce background and to detect atoms with a low horizontal velocity, which are needed for such an experiment. Our recent measurement results on the collimation of the hydrogen beam to 2 mm, the reduction of background and improvement of signal-to-noise and finally our first detection of atoms with velocities (<{72},hbox {ms}{^-1}) are presented. Furthermore, we show calculations, estimating the feasibility of the planned experiment and simulations which confirm that we can select vertical velocity components in the order of cm (hbox {s}^-1).

To further reduce the confinement loss of hollow-core anti-resonant fibers (HC-ARFs), broaden the low-loss operating bandwidth, and decrease the bending losses, this paper proposes a novel double-single-layer nested HC-ARF. The influence of structural parameters on its optical performance is analyzed using the full-vector finite element method, and the relevant structural parameters are optimized accordingly. The results indicate that, after optimizing the structural parameters, the HC-ARF exhibits extremely low confinement loss (on the order of 10^–8 dB/km) at the wavelength of 1.55 μm. When the bending radius is 10 cm, the bending loss is also very low (on the order of 10^–4 dB/km), which demonstrates an excellent bend-resistant property. Moreover, the HC-ARF possesses a very flat dispersion characteristic, with a low-loss operating bandwidth of approximately 945 nm, covering all the communication bands (O + E + S + C + L band).

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Cross section of the proposed double-single-layer nested HC-ARF and its Performance under the optimized structural parameters. This paper presents a new type of hollow - core anti - resonant fiber. The optical properties of this fiber, including confinement loss, bending loss and dispersion, etc., are numerically calculated by using the full-vector finite-element method. On this basis, the structural parameters of the fiber are optimized, and excellent optical properties are finally obtained.

We propose an dimer model consisting of two coupled microwave cavities with each cavity containing a two-level atom and a YIG sphere placed in the biased magnetic field. We use the semiclassical approximation and quantum master equation to investigate the delocalization–localization transition of the system. We find the sharp transition and the great photon localization under lower excitation. We also find that increasing initial photon number and magnon excitation can facilitate the localization. We also investigate the local second-order photon correlations to reflect the localization. The work suggests a new platform for studying the delocalization–localization transition of photons in cavity optomagnonic systems, with potential applications in quantum information processing. The article also discusses the experimental relevance of the model parameters.

We conducted a study on high-harmonic generation (HHG) in mixed gases, specifically Ar–Ne or Ar–Kr, with the aim of investigating the impact of ionization rate and neutral dispersion on the HHG process. Our focus was on understanding how these factors influence the HHG process when using gases with low and high ionization potentials. Based on phase-matched high-order harmonic generation in pure Ar gas, our investigation shows that the influence of plasma dispersion and neutral dispersion can be varied independently in mixed gas while the laser intensity is kept constant. Our results reveal that the addition of low ionization potential gases, such as Kr, to the Ar gas leads to a more rapid reduction in phase matching, due to the strong effects of ionization. The observed experimental outcomes align well with our theoretical calculations. This study provides valuable insights into the interplay of ionization rate and neutral dispersion in high-harmonic generation and the special requirement of the controlling of laser intensity for phase-matched harmonic generation. The findings contribute to a deeper understanding of the underlying dynamics and offer practical considerations for optimizing HHG properties.

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