Annalen der Physik最新文献

With advances in device miniaturization, understanding and manipulating nanoscale hot electron dynamics in semiconductors is recognized as an essential factor for improving performance and energy efficiency in optoelectronics and logic devices in the post-Moore era. This work demonstrates an effective strategy to modulate hot electron dynamics through nonequilibrium phonon excitations, utilizing first-principles-based mode-resolved electron-phonon coupled Boltzmann transport equation calculations. Two different phonon-mediated pathways for perturbing hot electron relaxation dynamics in doped semiconductors are illustrated, i.e., high-frequency optical phonons (e.g., longitudinal optical phonons in GaN) and low-frequency acoustic phonons, both of which exhibit strong coupling with electrons. While exciting high-frequency optical phonons to significant nonequilibrium states can quickly reheat and elevate electron temperatures, their rapid energy decay to other phonons fails to continuously slow down the subsequent hot electron relaxation. In contrast, the weak coupling of low-frequency acoustic phonons with other phonons facilitates the excitation of long-lived phonon nonequilibrium, which effectively prolongs the hot electron relaxation process from a few to tens of picoseconds for GaN, AlN, and Si. These findings reveal a general mechanism to modulate hot electron dynamics in device semiconductors, offering promising approaches to enhance the energy efficiency of advanced nanoscale devices.

The effect of structural disorder on the electrical transport is systematically studied in Bi₂Se₃-Fe₃O₄ nanograin-bulk thermoelectric materials. Keeping the characteristics of the Bi₂Se₃ matrix under control allows to evidence the role of localization and surface interaction in electronic transport in bulk nanostructured thermoelectric composites. Nanograin Bi₂Se₃-Fe₃O₄ bulks present an enhanced thermoelectric performance compared to Bi₂Se₃ and enable the realization of linear magnetoconductance at low temperatures in composite bulks. With the addition of Fe₃O₄, a crossover from positive to negative magnetoconductance is realized, more enhanced in c-axis textured samples. The observations are compatible with the presence of high mobility carriers at the Bi₂Se₃-Fe₃O₄ interfaces of the material.

The Gödel universe is considered within the context of the local limit of nonlocal gravity. This theory differs from Einstein's general relativity (GR) through the existence of a scalar susceptibility function $��S�\left(�x�\right)�$ that is a characteristic feature of the gravitational field and vanishes in the GR limit. It is shown that Gödel's spacetime is a solution of the modified gravitational field equations provided $�S$ is a constant, in conformity with the spatial homogeneity of the Gödel universe.

The Schmidt numbers quantify the entanglement degree of quantum states. Quantum states with high Schmidt numbers provide a larger advantage in various quantum information processing tasks compared to quantum states with low Schmidt numbers. A Schmidt number criterion is derived based on the trace norm of the correlation matrix obtained from symmetric measurements. It is showed that the result is more effective than and superior to existing Schmidt number criteria by detailed examples.

Recent pioneering experimental developments in measuring the superconducting energy gap Δ(T) in compressed sulfur using tunneling spectroscopy (Du et al., Phys. Rev. Lett. 133, 036002 (2024)) initiate an interest in better understanding the real atomic structure and superconducting properties of this element at high pressure. Here, available experimental data on highly compressed sulfur are analyzed, and, from the Δ(T) data reported by Du et al. (2024), the specific heat jump at the transition temperature is extracted. For a better understanding of materials structure at high pressure, here we propose a new approach that is the X-ray diffraction size-strain mappping of a sample in a diamond anvil cell. These size-strain maps are revealed for pressurized sulfur herein. Finally, it is found that the Debye temperature Θ_D and the electron-phonon coupling constant λ_e-ph, which are extracted from the temperature-dependent resistance reported by three independent research groups, are in excellent agreement with each other. The results show that superconducting sulfur exhibits a moderate level of nonadiabaticity, 0.04 ≤ Θ_D/T_F ≤ 0.20 (where T_F is the Fermi temperature), which is similar to MgB₂, pnictides, cuprates, La₄H₂₃, ThH₉, H₃S, LaBeH₈, and LaH₁₀.

Heusler compounds, particularly half-Heuslers, have been emerging as promising thermoelectric materials due to their high performance and mechanical robustness. This perspective summarizes the vacancy-filling strategy as a novel approach to enhance thermoelectric performance in thermoelectric Heusler compounds. By partially occupying the 4d Wyckoff sites, this strategy modifies crystal symmetry, tailors band structures, and introduces mass/strain fluctuations, significantly reducing lattice thermal conductivity. The perspective highlights how vacancy-filling bridges half-Heusler and full-Heusler phases, enabling high thermoelectric performance while uncovering exotic physical phenomena.

This study explores the dynamics of a Driven Time-Dependent Jaynes–Cummings (DTDJC) model, in which the atom and the field are influenced by an external classical field with time-varying amplitude modulation. By applying a series of unitary transformations and establishing suitable conditions for the time-dependent parameters of the system, the Hamiltonian operator is transformed into one representing a system not driven by an external field, namely a Free TDJC (FTDJC) system. This mapping allows us to determine, in both the time-independent and time-dependent cases, forms of the pumping modulating the field and the atomic population that are amenable to exact analytical solution. The effects of an off-resonance parameter emerging from the analytical solution of the model and the intensity of the classical pumping field on the dynamics of the atomic population are investigated. The exact solution allows us to reveal a rich dynamics of the system (including long-time super-revivals) that could be of use in future quantum technologies.

The thermal behavior of quantum correlations is explored in a two-qubit system based on nitrogen-vacancy (NV) centers, using Local Quantum Fisher Information (LQFI), Local Quantum Uncertainty (LQU), and concurrence as quantifiers. These results show that entanglement, measured byconcurrence (CE), decays rapidly with increasing temperature, whereas coherence-based measures such as LQFI and LQU display greater resilience. The strength of zero-field splitting plays a key role in shaping quantum correlations, significantly suppressing entanglement at higher values while helping to preserve coherence. External magnetic and electric fields further influence these dynamics–magnetic fields tend to suppress entanglement, while electric fields accelerate its degradation. Dipole–dipole interactions enhance the initial quantum correlations but have a limited effect on their thermal decay. Overall, these findings underscore the robustness of coherence-based quantum resources and suggest that, while dipole–dipole coupling is more effective at regulating quantum correlations, optimal tuning of system parameters can significantly improve both the generation and preservation of these correlations at finite temperatures.