Annalen der Physik最新文献

The formation and stability of solids and molecules is not possible without chemical bonds, which are divided into covalent, ionic, metallic, and van der Waals bonds. A special type of intermolecular bond is hydrogen bonding, which plays a crucial role for chemical, biological, and physical processes. However, hydrogen shows a far more complex behavior when it is present in solids. In this paper, it is shown that the chemical bonding of hydrogen atoms and molecules extends far beyond the simple picture of conventional, ionic, covalent, and multicenter bonds. The interaction of H with its host material is particularly important for hydrogen storage in metallic materials such as $��{\mathrm{Ti}}_3�C_2�$ MXenes. Hydrogen atoms and $�H_2$ molecules form multicenter bonds in $��{\mathrm{Ti}}_3�C_2�$. On the surface and between two $��{\mathrm{Ti}}_3�C_2�$ sheets this is limited to the formation of H–Ti bonds. However, H and $�H_2$ on interstitial sites form multicenter bonds not only with nearest neighbor Ti atoms but also with carbon atoms. Interestingly, the H–C bonds are characterized by the formation of s–p hybrid orbitals. For $�{}_{}$

A driven-dissipative system is considered, consisting of an atomic Bose-Einstein condensates loaded into a 2D Hubbard lattice and coupled to a single mode of an optical cavity. Due to the interplay between strong, repulsive atomic interaction and the atom-cavity coupling, the system exhibits several phases of atoms and photons including the atomic superfluid (SF) and supersolid (SS). The dynamical behavior of the system, where dissipation is included by means of Lindblad master equation formalism. Due to the discontinuous nature of the Dicke transition for strong atomic repulsion, extended co-existence region of different phases are found. The resulting switching dynamics are investigated, particularly between the coexisting SF and SS phases, which eventually becomes damped by the dissipation.

A hybrid system that combines cavity magnonics and cavity optomechanics is proposed to facilitate the generation of long-distance entanglement and enable one-way steering between magnons and phonons. This configuration involves two directly coupled cavities, with one interacting with magnons and the other coupling with a mechanical oscillator (i.e., phonons). By driving the microwave cavity with a weak squeezed vacuum field generated by a flux-driven Josephson parametric amplifier, entanglement and one-way steering can be further enhanced. Moreover, the results demonstrate that magnon–phonon entanglement and one-way quantum steering exhibit robustness against temperature variations, which has significant implications for quantum information processing and storage.

Quantum electrodynamical density functional theory is applied to obtain the electronic density, spin polarization, as well as orbital and spin magnetizations of square periodic arrays of quantum dots or antidots subjected to the influence of a far-infrared cavity photon field. A gradient-based exchange-correlation functional adapted to a 2D electron gas in a transverse homogeneous magnetic field is used in the theoretical framework and calculations. The obtained results predict a non-trivial effect of the cavity field on the electron distribution in the unit cell of the superlattice, as well as on the orbital and spin magnetizations. The number of electrons per unit cell of the superlattice is shown to play a crucial role in the modification of the magnetization via the electron–photon coupling. The calculations show that cavity photons strengthen the diamagnetic effect in the quantum dot structure, while they weaken the paramagnetic effect in the antidot structure. As the number of electrons per unit cell of the lattice increases, the electron–photon interaction reduces the exchange forces that will otherwise promote strong spin splitting for both the dot and the antidot arrays.

Neutron Star Mergers

When two neutron stars revolve around each other, they emit gravitational waves which drives them – initially very subtly but in the end very violently – towards a collision. In such a collision, neutron star matter gets ejected into space where it forms heavy elements via the “rapid-neutron capture process”. The freshly synthesized, initially radioactive nuclei power electromagnetic transients called “kilonovae” that are observable in a merger's aftermath. In article 2200306, Stephan Rosswog and Oleg Korobkin discuss today's state-of-the-art of this active research field.

The conservation of spectral asymmetry is a fundamental feature of the ideal four-wave mixing process as it exists in a medium combining quadratic chromatic dispersion and third-order nonlinearity. The robustness of this invariant in an experimental configuration where the excitation conditions of an optical fiber are sequentially updated, mimicking infinite propagation is tested in this paper. This theoretical and experimental study reveals the high sensitivity of the asymmetry to very slight deviations from the ideal case, and the idealized system behaves as an intermediate case between the ideal case of noncascaded four-wave mixing and propagation in a system governed by the nonlinear Schrödinger equation is shown.

Recently new methods have been introduced to investigate the non-renormalization properties of the anomalies at a non perturbative level and in presence of a lattice. The issue is relevant in a number of problems ranging from the anomaly-free construction of chiral lattice gauge theory with large cut-off to the universality properties observed in transport coefficients in condensed matter systems. A review of main results and future perspectives is presented.

The development of the nuclear industry has stimulated research in uranium extraction from seawater (UES) by adsorption. However, in practical applications, it's hard to equip various ion concentration measurement instruments for real-time characterizing uranium adsorption capacity. Given the radioactive property of uranium, if only a Geiger counter is possessed, how it can be utilized to rapidly evaluate uranium adsorption in the adsorbent? This study proposes the Geiger-Uranium-Distance model, which establishes correlations among Geiger counter readings, uranium adsorption capacity, and distance, thereby offering a viable approach. While maintaining a constant radius for the adsorbent stack point, during the laboratory phase, the average molecular mass (M_A) and the k_Gg(z) values of the original adsorbent are determined. In practical applications, the surrounding radiation background G_E (µSv h⁻¹) is detected. Subsequently, the Geiger counter is vertically positioned above the stacked point of adsorbent after uranium adsorption. Utilizing the measured radiation intensity value G (µSv h⁻¹), and employing the equation $��G��=�k_G��g��\left(�z�\right)��\frac{Q_e}{�1�+�M_A�Q_e�}�+�G_E�$, the uranium adsorption capacity Q_e can be obtained.

This paper proposes a 32-tupling frequency millimeter-wave (MMW) filter-free system based on four Mach-Zehnder Modulators (MZM) connected in parallel and cascaded with a simple radio-fiber (RoF) link structure. The four MZMs are all at the maximum transmission point (MATP), and the radio frequency (RF) driving voltage phase difference between MZMs is π /2. The center carrier is suppressed by using an optical attenuator (OATT) and an optical phase shifter (OPS). Two parallel MZMs can generate ±8th order and ±12th order optical sidebands, and the ±4th order optical sidebands can be suppressed by adjusting the modulation index m of the MZM, using cascaded two dual-parallel MZMS(DPMZM) and the phase difference of the RF signal source is π/4 to generate ±16th order optical sidebands. The theoretical analysis and simulation experiments are performed for the scheme proposed in this paper. The results show that the simulated and theoretical values of the optical sideband suppression ratio (OSSR) for ±16th order optical sideband signals are 60.02 and 59.96 dB, respectively, and the simulated and theoretical values of the RF sideband suppression ratio (RFSSR) for the 32-tupling MMW signal are 56.34 and 53.94 dB, respectively.