Advanced Physics Research最新文献

Susceptibility Parameters for Perpendicularly Moving Metasurfaces

This front cover illustrates customizable electromagnetic responses from moving metasurfaces. In article number 2400073, Hongsheng Chen, Zuojia Wang and co-workers explain how the susceptibility parameters transform when a metasurface moves perpendicularly towards the sources. The duality-matching condition for moving-invariant behaviors is derived. The absorption and chirality performance can be well preserved when the designed metasurfaces move quickly.

Topological insulator nanostructures became an essential platform for studying novel fundamental effects emerging at the nanoscale. However, conventional nanopatterning techniques, based on electron beam lithography and reactive ion etching of films, have inherent limitations of edge precision, resolution, and modification of surface properties, all of which are critical factors for topological insulator materials. In this study, an alternative approach for the fabrication of ultrathin Bi₂Se₃ nanoribbons is introduced by utilizing a diamond tip of an atomic force microscope (AFM) to cut atomically thin exfoliated films. This study includes an investigation of the magnetotransport properties of ultrathin Bi₂Se₃ topological insulator nanoribbons with controlled cross-sections at ultra-low 14 mK) temperatures. Current-dependent magnetoresistance oscillations are observed with the weak antilocalization effect, confirming the coherent propagation of 2D electrons around the nanoribbon surface's perimeter and the robustness of topologically protected surface states. In contrast to conventional lithography methods, this approach does not require a highly controlled clean room environment and can be executed under ambient conditions. Importantly, this method facilitates the precise patterning and can be applied to a wide range of 2D materials.

In this study, the performance of memristive devices made of oxygen-deficient HfO₂ films is investigated when exposed to various electrical pulse stimulations. The devices exhibited signs of fatigue with the number increasing of a fixed frequency pulse, mirroring the synaptic adaptation to repeat stimuli. Interestingly, the synaptic behavior can be highly simulated by logic function, and the pulse frequency and magnitude play different roles in changing the synaptic curves. Only pulses with certain quantized frequencies can reshape the synaptic current response curve. In addition, a similarity is observed between the frequency stability of these devices and the biological lifespan in response to external stimuli. These observations strengthen the case for the potential of memristors in emulating cognitive functions.

Chiral hybrid organic-inorganic perovskites (HOIPs) are widely investigated due to their superior chiroptical and chiral spintronic properties. Research on the enhancement of chiroptical performance is highly important for the real application of chiral HOIPs. This work employed a rare earth doping strategy to increase the magnetic transition dipole moment of chiral 2D HOIPs R-/S-NPB (NPB = 1-(1-naphthyl) ethylammonium lead bromide). Doping with Eu³⁺ does not change the original layered NPB microstructure, and R-/S-NPB-Eu exhibited the magnetic dipole-allowed transition luminescence of Eu³⁺ at 594 nm (⁵D₀→⁷F₁). Circular polarized luminescence (CPL) spectra combined with theoretical calculations and transient photoluminescence measurements indicated that the introduction of Eu³⁺ can enhance the magnetic transition dipole moment of R-/S-NPB, thus resulting in an unprecedented g_lum of 0.05. To the best of our knowledge, this is the highest value for chiral perovskite films. This work combines the unique and superior optoelectronic properties of rare-earth ions with chiral perovskite and develops an efficient strategy to increase its anisotropy factor, which can accelerate the development of chiral optoelectronics and spintronics towards real application.

Organic nonlinear optical (NLO) crystals have emerged as efficient room-temperature emitters of broadband THz radiation with high electric field strengths. Although initially confined to high-pulse-energy excitation in the millijoule range with kHz rates, recent efforts have focused on tailoring the physical properties of organic NLO materials for compatibility with popular MHz-rate telecommunication wavelength lasers emitting nanojoule energy pulses. This is motivated by the large potential of such crystals for more portable and user-safe spectroscopic systems, additionally complemented by their room-temperature field-sensitive THz detection capabilities. In this work, the MHz-rate operation of the organic crystal PNPA ((E)-4-((4-nitrobenzylidene)amino)-N-phenylaniline), which was recently discovered through data mining algorithms and reported to surpass the conversion efficiency of rivaling NLO crystals at 1 kHz repetition rate is demonstrated. Using a compact 200 mW Er:fiber laser producing 18 fs pulses at 50 MHz repetition rate, the THz field generation and detection capabilities of PNPA via performing gas phase spectroscopy in the 1.3–8.5 THz range are demonstrated. A dynamic range of 40 dB over 3.6 s and 70 dB over 2 h is obtained. The work extends the family of organic crystals compatible with telecommunication-wavelength excitation using nJ pulses for spectroscopy beyond 5 THz.

Epsilon-Near-Zero Media

Epsilon-near-zero (ENZ) media have garnered widespread attention due to their unique electromagnetic properties, which result in distinctive features and phenomena. Among these, ENZ supercoupling and tunneling, a notable engineering application of ENZ media, is showcased on the cover. Electromagnetic waves propagate through ENZ media without experiencing phase changes, allowing them to bypass obstacles and sharp bends effortlessly. Y. Li and co-workers begin their review, 2400070, with an exploration of the fundamental properties of the waveguide ENZ media and then introduce the design principles of different ENZ-based electromagnetic devices. The review concludes with the challenges and potential development directions encountered by ENZ media in the realm of electromagnetic applications.

Terahertz frequencies locating between microwave and infrared regions can record and process optical information for next-generation information technology such as 6G communication. Metasurfaces, as emerging planar optical components built with micro- or nanostructures, enable precise control, and manipulation of electromagnetic waves from near fields to far fields. These subwavelength artificial structures can be engineered to exhibit specific polarization responses, thus holding significant potential for applications in polarization detection. In the terahertz (THz) region, polarization information is crucial for identifying and analyzing the properties of materials in the terahertz. In this review, we focus on recent advances in terahertz metasurfaces for polarization manipulation and detection, including principles and emerging applications. New polarization detection methods such as polarization state conversion, polarization-selective absorption, polarization-selective focusing, and vector beam construction are discussed. Finally, it is concluded with a few perspectives on emerging trends and existing challenges in the fields of terahertz polarization manipulation and detection.

Photothermal sensing is crucial for the creation of smart integrated devices. All-inorganic metal halide perovskites with the formula CsPbX₃ (X═Cl, Br, I) have excellent photo-physical performance, offering exciting opportunities for flexible electronics. Hence, a supersaturated precipitation strategy is proposed for the preparation of salt-shelled metal halide solids. The well-designed CsPbX₃@MX (M═K, Cs) products exhibit bright narrow visible emissions and favorable thermal stability up to 195 °C. Co-doping with Ni²⁺ and Mn²⁺ ions, the CsPbCl₃@KCl products have realized dual-mode thermometry. Utilizing the blue emission from the CsPbCl₃ host and the red emission from the Mn²⁺ ion, a fluorescence intensity ratio technique is obtained to monitor the temperature of good stability and repeatability. Based on the regular fluorescence decay of Mn²⁺ ions with rising temperature, the lifetime of Mn²⁺ ions can also be used for temperature sensing. It is believed that such stable metal halides with dual-mode thermometry will provide a new sight for optical thermometers and, more importantly, will unleash the possibility of a broad variety of applications in lightweight and integrated functional devices.