Annalen der Physik最新文献

A generalization of the classical nonrelativistic Störmer problem is considered, describing the motion of charged particles in a purely magnetic dipole field, by taking into account the effects of the dissipation, assumed to be of friction type, proportional to the velocity of the particle, and of the presence of stochastic forces. In the presence of dissipative/stochastic effects, the motion of the particle in the magnetic dipole field can be described by a generalized Langevin type equation, which generalizes the standard Lorentz force equation. A detailed numerical analysis of the dynamical behavior of the particles is performed in a magnetic dipolar field in the presence of dissipative and stochastic forces, as well as of the electromagnetic radiation patterns emitted during the motion. The effects of the dissipation coefficient and of the stochastic force on the particle motion and on the emitted electromagnetic power are investigated, and thus a full description of the spectrum of the magnetic dipole type electromagnetic radiation and of the physical properties of the motion is also obtained. The power spectral density of the emitted electromagnetic power is also obtained for each case, and, for all considered Störmer type models, it shows the presence of peaks in the radiation spectrum, corresponding to certain intervals of the frequency.

Chloride salts are used as the heat transfer (HT) media for the third-generation concentrated solar power (CSP). Challenges such as localized high-temperature and uneven wall temperature within the absorber tube (AT) persist. Furthermore, the HT of mixed convection (MC) for molten salt is different from that for common fluid. To address these issues, an AT featuring turbulent MC is proposed and numerically analyzed. Furthermore, the performance of AT is evaluated under various operational parameters. Results indicate that the secondary flow (SF) induced by buoyancy force (BF) generates two vortices, enhancing salt mixing and HT. Consequently, there is a significant improvement in temperature uniformity, accompanied by a substantial reduction in the maximum temperature. Compared to forced convection (FC), the maximum temperature as well as temperature gradient for MC is reduced by up to 242.73 K. Additionally, there is an increase of 3.57–16.76% in the Nusselt number and a 5.98%–30.07% increase in the friction factor. The thermal performance factor (TPF) ranges from 1.016 to 1.070. Moreover, the maximum reduction in the entropy generation rate (EGR) is 16.52%, and the highest enhancement in exergy efficiency (EE) reaches 4.68%. This study provides practical insights for the development of more efficient and secure chloride salt AT.

In the momentous tide of advanced medical physics and neuroimaging capabilities that have transformed neurological and neurosurgical clinical practice and research, it is crucial to mobilize this effort against incurable pathologies, such as glioblastoma (GBM). GBM is a malignant WHO Grade 4 brain tumor that inevitably recurs post-operatively and is fatal. With diffusion tensor imaging, tumor cells' occult infiltration of white matter tracts in the brain can be detected, with insight into the trajectory that GBM progression will take. However, an extra step is needed to predict that trajectory, which is a separate endeavor from only visualizing it. Mathematical modeling of glioma cell “diffusion” within the brain has been broadly reported, but with limited practical application. To improve predictive modeling for refining treatment, diffusion is reviewed from a physics and mathematical framework, beginning with contributions from Joseph Fourier and proceeding to the modern day. This review then focuses on drawing a distinctive connection to advanced medical physics and neuroimaging capabilities and how they can be operationalized to better model GBM progression.

The nature of quantum jumps occurring between macroscopic metastable states of light in the open driven Jaynes–Cummings model is investigated. It is found that, in the limit of zero spontaneous emission considered in [H. J. Carmichael, Phys. Rev. X 5, 031028 (2015)], https://doi.org/10.1103/PhysRevX.5.031028 the jumps from a high-photon state to the vacuum state entail two stages. The first part is coherent and modelled by the localization of a state superposition, in the example of a null-measurement record predicted by quantum trajectory theory. The underlying evolution is mediated by an unstable state (which often splits to a complex of states), identified by the conditioned density matrix and the corresponding quasi probability distribution of the cavity field. The unstable state subsequently decays to the vacuum to complete the jump. Coherence in the localization allows for inverting the null-measurement photon average about its initial value, to account for the full switch which typically lasts a small fraction of the average cavity lifetime; an asymptotic law for the jump time is established in high-amplitude bistability. This mechanism is contrasted to the jumps leading from the vacuum to the high-photon state in the bistable signal. Spontaneous emission degrades coherence in the localization, and prolongs the jumps.

Superconducting interfaces have recently been demonstrated to contain a rich variety of effects that give rise to sizable thermoelectric responses and unexpected thermal properties, despite traditionally being considered poor thermoelectrics due to their intrinsic electron–hole symmetry. Different mechanisms driving this response in hybrid normal-superconducting junctions, depending on the dimensionality of the mesoscopic interface, are reviewed. In addition to discussing heat-to-power conversion, cooling, and heat transport, special emphasis is put on physical properties of hybrid devices that can be revealed by the thermoelectric effect.

Recently, cold atoms mixtures have attracted broad interest due to their novel and exotic quantum effects with respect to single-component systems. In this study, the focus is on massive many-vortex states and their dynamics. Vortex configurations characterized by the same discrete rotational symmetry are investigated when confined within topologically nonequivalent geometries, and the relative stability properties at varying number of vortices and infilling mass are highlighted. It is numerically shown how massive many-vortex systems, in a mixture of Bose–Einstein condensates, can host the bosonic tunneling of the infilling component both in a disordered way, with tunneling events involving two or more close vortices, or in an almost-periodic way when the vortices are organized in persisting necklaces or star-lattices. The purpose is to explore a variety of situations involving the interplay between the highly-nonlinear vortex dynamics and the inter-vortex atomic transfer, and so to better understand the conditions for the onset of Josephson supercurrents in rotating systems, or to reveal phenomena that can be of interest for a future application, e.g., in the context of atomtronics.

Unconventional magnon and photon blockade have attracted significant research interest for their ability to generate single-particle sources in hybrid quantum systems, particularly in cavity magnonics. In this work, a scheme is presented to investigate the effect of Barnett effects in the nonreciprocal blocked of magnons and photons within a spinning microwave magnomechanical system with a squeezed input drive of the magnonic mode. The effects of thermal noise, the amplitude of a probe field, and the magnetic-dipole coupling strength are realized using the weak-coupling regime. Using the Mandel parameter, the nonclassicality of the system is discussed. Additionally, the time evolution of the second-order correlation function is examined.

The open quantum dynamics of a two-qubit quantum dot system is investigated initially prepared as thermal state and exposed to an Ohmic bosonic reservoir, modeling it as a prototype quantum processor. By integrating local and interaction Hamiltonians, field-induced couplings, and thermal effects, we derive the system's thermal state and analyze its evolution using quantum measures: concurrence, Bell nonlocality, energy fluctuations, and quantum speed limit (QSL) time. Results reveal that strong field-induced coupling enhances and preserves quantum correlations, which otherwise vanish abruptly beyond a critical coupling strength. Conversely, energy fluctuations and the QSL time are suppressed for weak coupling but increase significantly in the strong coupling regime. Higher temperatures are shown to uniformly accelerate the dissipation of quantum correlations. Furthermore, it is found that while weak splitting strength allows for tunable correlations, strong splitting enhances initial correlations and energy fluctuations at the cost of suppressing the QSL. These findings demonstrate the potential of coupled quantum dots as tunable two-qubit processors, providing a guide for precise control over their quantum and thermal properties.

Topological Heusler ferromagnets have emerged as a promising material platform for realizing a large anomalous Nernst effect (ANE) due to their intrinsic Berry curvature. This work reports a significantly enhanced ANE in polycrystalline bulk Co₂MnAl_1-xSi_x, enabled by synergistic tuning of atomic ordering and Fermi level via Si substitution. A large anomalous Nernst thermopower of 4.9 µV K⁻¹ and an anomalous Nernst conductivity of 1.46 A m⁻¹ K⁻¹ at 300 K are obtained in Co₂MnAl_0.69Si_0.31. Furthermore, A centimeter-sized bulk Nernst thermoelectric generator has been developed using Co₂MnAl_0.69Si_0.31 as the legs, which delivers an output voltage of 2.2 mV and a maximum power of 7.7 µW under a temperature difference of 15 K. These results highlight the potential of scalable, high-performance polycrystalline topological magnets for transverse thermoelectric applications and pave the way for practical integration of ANE-based devices.

Topological modes are well-known for their robust and directional wave transportation. However, the symmetric Lamb and shear horizontal waves are precious in topological wave systems. These guided waves in a plate are promising in fields like wave communications and nondestructive testing. In this work, a valley topological phononic crystal plate that supports symmetric plate modes, e.g., zero-order symmetric Lamb (S0) and fundamental shear horizontal (SH0) waves, is constructed. The proposed structure is efficient for controlling the mode conversion between S0 and SH0 modes. The mode conversion is governed by the weight ratio of displacement components of the topological edge states (TES) branches. The remarkable feature, i.e., robustness, of TES of symmetric plate modes is also demonstrated. These results provide an efficient way to control the wave components feasibly.