Advanced Physics Research最新文献

The dynamic regulation of thermal radiation in the mid-infrared region is technologically important in diverse applications such as thermal management and camouflage. However, there is a notable lack of research on the combination of infrared radiators and memristors, which can maintain previous states or modes without extra power consumption. Here, a memristive mid-infrared radiator, where graphene nanoribbon grating serves simultaneously as a floating gate for charge storage and a tunable infrared nanoantenna for thermal radiation is proposed. This design enables precise and fast modulation, low power consumption, and scalability. Even a small change of one attocoulomb in the stored charge can produce a 1-µm peak shift in the absorption peak. This work provides a platform for a memristive infrared thermal radiator that can be further exploited for electrochromic glazing or on-chip radiative cooling.

In spin wave (SW) devices, the modulation of SWs for computational units is necessary, imposing extremely high demands on material systems. In this study, high-quality epitaxial-grown spinel γ-Fe₂O₃ thin films on conductive Nb-doped SrTiO₃ substrates, achieving fast-speed, high-frequency, and long-distance SW propagation in this ferrimagnetic material, are developed. A novel two-step film growth technique using pulsed laser deposition is proposed and optimized, and the damping constant, exchange stiffness, and anisotropies of γ-Fe₂O₃ are determined. Compared to reported semiconductor magnetic materials, these epitaxial-grown γ-Fe₂O₃ thin films exhibit a significantly lower damping constant of 10⁻², representing a substantial advancement. Using finite-difference calculations, SW propagation is simulated, and vital information on transmission distance and dispersion curves is obtained. Experimental results show excellent agreement with these simulations. By applying a voltage to both sides of the conducting substrate, current across the film and SW device, resulting in the frequency shift of the SWs, is generated. These results demonstrate that high-quality γ-Fe₂O₃ films developed through the two-step growth method can efficiently propagate SWs, offering possibilities for various modulation methods in SW-based computing devices. This study positions spinel γ-Fe₂O₃ as a promising ferrimagnetic candidate for future applications in efficient SW modulation within computational systems.

Nitrogen-vacancy (NV) centers in diamonds are one of the most promising systems for quantum technologies, including quantum metrology and sensing. A promising strategy for the achievement of high sensitivity to external fields relies on the exploitation of large ensembles of NV centers, whose fabrication by ion implantation is upper limited by the amount of radiation damage introduced in the diamond lattice. In this work an approach is demonstrated to increase the density of NV centers upon the high-fluence implantation of MeV N²⁺ ions on a hot target substrate (>550 °C). The results show that with respect to room-temperature implantation, the high-temperature process increases the vacancy density threshold required for the irreversible conversion of diamond to a graphitic phase, thus enabling to achieve higher density ensembles. Furthermore, the formation efficiency of color centers is investigated on diamond substrates implanted at varying temperatures with MeV N²⁺ and Mg⁺ ions revealing that the formation efficiency of both NV centers and magnesium-vacancy (MgV) centers increases with the implantation temperature.

Transparent conducting oxides, like indium tin oxide, enable lateral charge carrier transport in silicon heterojunction solar cells. However, their deposition can damage the passivation quality in the solar cell. This damage during the sputter deposition is a complex issue that has not been fully understood, particularly in various silicon-based materials like amorphous silicon, polycrystalline silicon, or nanocrystalline silicon carbide. The degradation in passivation quality observed in, for example, amorphous silicon is not only explainable by UV light degradation. This study explores the origin of this degradation based on the example of hydrogenated nanocrystalline silicon carbide by combining simulations with experimental analyses. It delves into potential sources of damage during the sputtering process and determines that neither primary nor secondary effects from plasma luminescence or electron bombardment are likely contributors to the damage. Similarly, the implantation of ions, as well as the creation of vacancies and ionization of lattice atoms, are also considered improbable causes. It is, however, proposed that the transfer of energy to the crystalline silicon interface via phonons can factor into the degradation of the passivation quality. This transfer might be a plausible explanation for the damage observed in the passivation layers during the sputtering process.

Metasurfaces, as 2D artificial electromagnetic materials, play a pivotal role in manipulating electromagnetic waves by controlling their amplitude, phase, and polarization. Achieving this control involves designing subwavelength meta-molecules with specific geometries and periodicities. In the context of microfluidic metasurfaces, optical properties can be dynamically modulated by altering either the geometric structure of liquid meta-molecules or the refractive index of the liquid medium. Leveraging the fluidity of liquid materials, microfluidic metasurfaces exhibit remarkable performance in terms of reconfigurability and flexibility. These properties not only establish a cutting-edge research area but also broaden the scope of applications for active metasurface devices. Additionally, the integration of metasurfaces within microfluidic systems has led to novel functionalities, including enhanced particle manipulation and sensor technologies. Compared to conventional solid-material-based metasurfaces, microfluidic metasurfaces offer greater design freedom, making them advantageous for diverse fields such as electromagnetic absorption, optical sensing, holographic displays, and tunable optical meta-devices like flat lenses and polarizers. This review provides insights into the characteristics, modulation techniques, and potential applications of microfluidic metasurfaces, illuminating both the current research landscape and promising avenues for further explorations.

Among promising applications of metal-halide perovskite, the most research progress is made for perovskite solar cells (PSCs). Data from myriads of research work enables leveraging machine learning (ML) to significantly expedite material and device optimization as well as potentially design novel configurations. This paper represents one of the first efforts in providing open-source ML tools developed utilizing the Perovskite Database Project (PDP), the most comprehensive open-source PSC database to date with over 43 000 entries from published literature. Three ML model architectures with short-circuit current density (J_sc) as a target are trained exploiting the PDP. Using the XGBoost architecture, a root mean squared error (RMSE) of 3.58 $$, R² of 0.35 and a mean absolute percentage error (MAPE) of 9.49% are achieved. This performance is comparable to results reported in literature, and through further investigation can likely be improved. To overcome challenges with manual database creation, an open-source data cleaning pipeline is created for PDP data. Through the creation of these tools, which have been published on GitHub, this research aims to make ML available to aid the design for PSC while showing the already promising performance achieved. The tools can be adapted for other applications, such as perovskite light-emitting diodes (PeLEDs), if a sufficient database is available.

A straightforward analytical approach is proposed for the design of minimally thin metal absorbers. Unlike traditional resonant design principles, where shape, size, and periodicity of a nanostructured film determine the absorption properties, this study uses only the thickness and permittivity (i.e., sheet conductivity) of the material at hand to demonstrate maximal absorption in the minimal possible thickness at any given wavelength in planar layers – guided by only the derived material-agnostic equations. An alternative mechanism is further proposed and experimentally demonstrated to obtain precise control over the sheet conductivity of metal films necessary for such designs using metal dilution, enabling the tuning of both the amplitude and the phase of reflected waves. Finally, the concept of “phase doping” is proposed and experimentally demonstrated, wherein an ultrathin metal layer is placed within the spacer of the absorber cavity, which spectrally tunes the absorption feature without changing the spacer thickness or participating in the absorption. By judiciously combining the dilution of the absorbing and phase layers, a multifunctional ultrathin absorber architecture is demonstrated with customizable amplitude, spectral position, and selectivity, all leveraging the same vertical stack. These findings are promising for the design of ultrasensitive detectors, thermal emitters, and nonlinear optical components.

The linear magnetoelectric (ME) characteristics of a quasi-1D spin-chain compound, FePbBiO₄, are reported. Two distinct antiferromagnetic (AFM) orders occurring at ≈23 K (T_N1) and 12 K (T_N2) are verified using magnetization, specific heat, and conspicuous dielectric (ε′) anomalies. A striking observation is that no pyrocurrent (I_py) is detected in the absence of magnetic field (H); however, H-induced ferroelectric polarization (P) at T_N1 and P unexpectedly partially switches or reverses below T_N2 as reproduced by applying positive and negative electric fields (E). The resulting magnetic field and temperature (H-T) phase diagram illustrates T-dependent H-induced spin reorientation and electric P. The interaction between T, H, spin dynamics, and lattice structures is pivotal and is qualitatively discussed and proposed as an explanation for the observed ME nature.

Materials featuring touching points, localized states, and flat bands are of great interest in condensed matter and artificial systems due to their implications in topology, quantum geometry, superconductivity, and interactions. In this theoretical study, the experimental realization of the dice lattice with adjustable parameters is proposed by arranging carbon monoxide molecules on a two-dimensional (2D) electron system at a (111) copper surface. First, a theoretical framework is developed to obtain the spectral properties within a nearly free electron approximation and then compare them with tight-binding calculations. This investigation reveals that the high mobility of Shockley state electrons enables an accurate theoretical description of the artificial lattice using a next-nearest-neighbor tight-binding model, resulting in the emergence of a touching point, a quasi-flat band, and localized lattice site behavior in the local density of states. Additionally, theoretical results for a long-wavelength low-energy model that accounts for next-nearest-neighbor hopping terms are presented. Furthermore, the model's behavior under an external magnetic field is theoretically examined by employing Peierl's substitution, a commonly used technique in theoretical physics to incorporate magnetic fields into lattice models. The theoretical findings suggest that, owing to the exceptional electron mobility, the highly degenerate eigenenergy associated with the Aharonov-Bohm caging mechanism may not manifest in the proposed experiment.

The magnetic phase transition is explored in CrSBr flakes through non-magnetic ion irradiation, revealing a novel method for magnetic control in two-dimensional (2D) materials. The rise and fall of the ferromagnetic phase is observed in antiferromagnetic CrSBr with increasing the irradiation fluence. The irradiated CrSBr shows ferromagnetic critical temperature ranging from 110 to 84 K, well above liquid N₂ temperature. Raman spectroscopy reveals phonon softening, suggesting the formation of defects. These findings not only highlight CrSBr's potential in spintronics, but also present ion irradiation as an effective tool for tuning magnetic properties in 2D materials, opening new avenues for the development of spintronic devices based on air-stable van der Waals semiconductors.