Annalen der Physik最新文献

In the present theoretical work, magnetic response of a tight-binding (TB) dimerized ring subjected to Aharonov–Bohm (AB) flux and environmental interactions is numerically explored. Specifically, an imaginary site potential on the odd lattice sites is introduced to represent physical gain and loss, while the even lattice sites remain unperturbed. The induced current resulting from the AB flux in both real and imaginary eigenspaces, aiming to enhance this current significantly by adjusting the gain/loss parameter ($�d$) is investigated. The analysis focuses on how exceptional points in the real and imaginary eigenenergy spaces contribute to notable increases in current at specific $�d$ values, and the emergence of purely real current when the imaginary current vanishes. How the dual behavior of energy spectrum (real and imaginary), converging to and diverging from zero energy, affects the enhancement of the current is discussed. Additionally, the interplay between the correlations of dimerized hopping integrals and the gain-loss parameter, which affects the current and highlights key features associated with these physical parameters, is studied. Furthermore, how system size impacts the findings is considered. The study may reveal unconventional characteristics in various loop configurations, potentially paving the way for new research directions.

The electronic transmission properties of two-terminal graphene nanoribbon (GNR) devices, featuring ring and ladder geometries with varying sizes, are investigated to understand the influence of explicit charge doping on their electrostatic control. The results indicate that explicit charge doping affects the device behavior, from single electron transport to resonant transport for different channels. When charge doping is applied, it induces quantum dot formation electrostatically, causing the ladder-type channel GNR with a channel length of 49.7 Å to function similarly to a quantum dot. Therefore, this smallest ladder type channel shows current oscillations which are attributed to single-electron tunneling. As the channel length increases in ladder-type devices, a current path develops within the channel, forming a conductive path in larger devices that results in significant current and eliminates the tunneling barrier effect. On the other hand, for the ring-shaped GNRs, it is found that the transport behavior gradually shifts from an antiresonant to a resonant transport regime with increasing radius under explicit charge doping. These results show a strong competition between quantum-confinement effects and quantum dot-to-electrode coupling for both geometries when explicit charge doping is applied.

This work examines the instantaneous lifetime dynamics of a positronium (Ps) atom under spherical confinement, influenced by a short laser pulse, and embedded in different plasma environments such as plasma-free (PF), Debye plasma (DP), quantum plasma (QP), and nonideal classical plasma (NICP). The effects of medium parameters-particularly the screening length, confinement radius, pulse frequency, and pulse strength are systematically analyzed. For the plasma interactions of the Ps atom, the work considers the screened Coulomb potential, exponential cosine screened Coulomb potential, and nonideal classical plasma potential. The corresponding wave equation is solved numerically using the tridiagonal matrix method. The effects of the short laser pulse are probed within the Runge–Kutta–Fehlberg formalism. Under the influence of the short laser pulse, the screening effects of plasma environments on the instantaneous lifetime of Ps are systematically examined in the time domain, and the functionalities of these environments are compared in detail. A similar analysis is also performed for the spherical confinement radius, as well as the strength and frequency of the short laser pulse. Significant influences and functional dependencies of the medium parameters and laser pulse on the instantaneous lifetime are identified. These results not only contribute to understanding the behavior of the Ps atom in complex environments but also provide a new perspective for controlled positronium applications in experimental plasma systems. The obtained findings offer new possibilities for engineering the lifetime dynamics of short-lived quantum structures, particularly Ps, in the context of laser-matter interactions and precise control of quantum systems in plasma environments. In this regard, they hold significant application potential across a broad spectrum ranging from antimatter physics to quantum optics.

The photonic spin Hall effect (SHE) is explored in a highly tunable Rydberg-based atomic system by leveraging the distinctive properties of Rydberg superatoms. These superatoms arise from strong dipole–dipole interactions and extended radiative lifetimes, resulting in collective excitations governed by the dipole blockade mechanism. An ensemble of three-level atoms in a cascade configuration models a medium in which each superatom acts as a coherent quantum entity. The photonic SHE shows strong dependence on the probe field Rabi frequency and atomic number density. At high Rabi frequencies, the blockade effect suppresses the photonic SHE, confining its occurrence to specific resonant conditions. In contrast, under weak probe excitation, the blockade influence diminishes, enabling an amplified photonic SHE response at resonant detuning due to increased light-matter interaction sensitivity. Reducing atomic number density further broadens the detuning range over which the photonic SHE occurs, indicating a transition toward a more sensitive, less resonance-constrained optical behavior. The effect of van der Waals interactions on the photonic SHE shift is also characterized. This expanded operational bandwidth demonstrates the potential of Rydberg-based systems for robust spin-optical control, particularly in scenarios where precise stabilization of the probe field frequency is experimentally challenging.

In this paper, an all-metal metamaterial and its reflection are analyzed. The electromagnetically induced reflection (EIR)-like effect is obtained by the electric field and surface current distribution of the resonant frequencies. Through discussing the structural parameters, the bound states in continuous (BIC) phenomenon is found. Measured in a microwave anechoic chamber, it is described that the measured result is basically consistent with the simulation result. All-metal metamaterial is simple, cheap, and easy to process, the research has potential applications on filtering, sensing.

A shortcut-to-adiabaticity is compared with a numerically optimized protocol for implementing a high-fidelity quantum gate on Rydberg atoms. The counterdiabatic method offers an analytical framework for accelerating high-fidelity gates by mimicking the time evolution of a counterdiabatic Hamiltonian using fast-oscillating fields. This approach is contrasted with a numerically optimized gate designed using the Boulder Opal platform. The numerically optimized gate achieves higher fidelities while demonstrating robustness against errors similar to that of the effective counterdiabatic gate. The study serves as an example of the performance of analytic shortcut-to-adiabatic-inspired protocols compared to brute-force numerical optimization techniques for state-of-the-art quantum computing platforms. It stresses the important role played by constraints on the optimized pulses in time and in amplitude that are crucial in determining the quality of the optimization method.

The earth-abundant tin sulfide (SnS) has emerged as an ecologically sustainable alternative for the thermoelectric community recently. However, its wide bandgap (≈46 k_BT) is unfavorable for electrical performance, while the high vapor pressure of the S often results in a relatively low yield of synthesis. In this study, a synergistic strategy is devised to optimize the thermoelectric performance of polycrystalline SnS prepared via a low-temperature solid-state synthesis method. First, silver doping increases the hole carrier concentration (n) to ≈10¹⁹ cm⁻³. Subsequently, through selenium alloying, a dual-effect can be achieved: the bandgap is narrowed to increase the doping efficiency, while atomic point defects are introduced to lower the thermal conductivity. Ultimately, the polycrystalline Sn_0.98Ag_0.02S_0.55Se_0.45 attains a maximum ZT value of ≈0.9 at 873 K. The study indicates that promising thermoelectric performance can be obtained by a rapid synthesis method through a series of meticulously designed optimization strategies. This achievement offers novel insights and paves the way for the development of sulfide-based thermoelectrics.

Mutual conversions between different entangled states play a significant role in quantum information processing (QIP), significantly boosting the versatility and robustness of quantum systems, and particularly paving the way for demanding specific entanglement forms. Reliable protocols are proposed for the deterministic mutual conversions between the three-logic-qubit W state and the three-logic-qubit Knill–Laflamme–Milburn state within a decoherence-free subspace (DFS), which utilizes weak cross-Kerr nonlinearity combined with X-homodyne measurement. In-depth analyses of both protocols confirm that they can achieve high fidelities and outstanding efficiencies by related feedback operations. Additionally, the protocols effectively suppress decoherence effects through the use of DFS, enabling the advanced development of practical QIP.