Advanced Physics Research最新文献

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.

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.

Metasurfaces have attracted progressive attention as 2D metamaterials in recent years. Due to the ability to manipulate the phase, amplitude, and polarization of electromagnetic waves, metasurfaces have become a feasible way to control the wavefront. Here, two main platforms for exciting multi-order diffraction beams in the far field based on metasurfaces, i.e., phase gradient metasurfaces (PGMs) and metagratings (MGs) are reviewed. First, the concept of generalized Snell's law (GSL) as well as the related works are presented. Then the connection between GSL and diffraction law is elaborated. The multi-order diffraction methods based on the combination of the two principles are introduced. Following the discussion on several kinds of PGMs platforms for achieving multiple beams, the physical mechanisms of MGs are reviewed and recent progress is summarized. Finally, the typical challenges are outlined and the future development directions are prospected.

I-III-VI semiconductor nanocrystals (NCs) have emerged as promising candidates in quantum-dot light-emitting diodes (QLEDs) due to their environmental-benign nature and capability for large-scale tunable emission as well as straightforward synthesis. However, the photoluminescence (PL) emission of I–III–VI type NCs, as reported in numerous studies, exhibits a broader full width at half maximum (FWHM), adversely affecting their color purity. This review delineates the advancements in the development of narrow-bandwidth I–III–VI NCs, focusing on their synthesis strategies, luminescence mechanisms, and applications in QLEDs. It concludes with a discussion on the challenges confronting narrow-bandwidth I–III–VI-based QLEDs and outlines potential strategies for improving device performance.

Epitaxially strain-engineered tetragonal (T)-like BiFeO₃ (BFO) is a multiferroic material with unique crystallographic and physical properties compared to its bulk rhombohedral parent. While the effect of this structural change on ferroelectric properties is understood, the influence on correlated antiferromagnetic (AFM) properties, especially with reduced film thickness, is less clear. Here, the AFM behavior of T-like BFO films 9–58 nm thick on LaAlO₃ (001) substrates fabricated by pulsed laser deposition was studied using conversion electron Mössbauer spectroscopy and X-ray diffraction. The key findings include: i) Ultrathin T-like BFO films (<10 nm) show a decoupling of magnetic and structural transitions, with the polar vector tilted 32 degrees from [001] in 9–13 nm films. ii) Films thinner than 13 nm exhibit no structural transition down to 150 K, with a Néel (T_N) transition at ≈290 K, ≈35 K lower than thicker films. Interestingly, the T_N scaling with thickness suggests realistic scaling exponents considering a critical correlation length for C-type AFM order, rather than G-type. The results show that finite size effects can tailor transition temperatures and modulate AFM wave modes in antiferromagnetic oxides, with implications for AFM spintronics for future information technologies.

Chemical Vapor Deposition

In the growth of two-dimensional transition metal dichalcogenide crystals, tuning the mix of physical mechanisms like thermodynamics and kinetics can enable phase engineering and shape control of such crystals for advanced applications. In their review article 2300146, W. Fu, K.E.J. Goh and co-workers provide an updated guidance for exploiting these physical strategies in the technique of chemical vapor deposition.

To further enhance the performance and understand the mechanism of InAs quantum dot (QD) laser under high temperature, both theoretically and experimentally it is investigated, the effects of the technique of the combination of direct n-type doping and modulation p-type doping, namely co-doping, in the active region for a wide temperature range over 165 °C. Through the comparison of co-doped, modulation p-type doped, direct n-type doped, and undoped QD lasers, it reveals that the co-doping technique provides a significantly reduced threshold current density across the whole temperature range and robust high-temperature operation. Furthermore, it is also observed that the effectiveness of co-doping in suppressing round-state quenching is comparable to that of p-doping. The improvements in the doping strategies are also revealed through the rate equation simulation of the lasers.

Luminescent nanothermometry emerges as a powerful tool for studying protein dynamics. This technique was employed to perform the first measurement of the temperature dependence of protein Brownian velocity, showcasing the illustrative example of enhanced green fluorescent protein (EGFP) across physiologically relevant temperatures (30−50 °C) and concentrations (40, 60, and 80 × 10⁻³ kg m⁻³). EGFP exhibited a concentration-dependent decrease in Brownian velocity, from (1.47 ± 0.09) × 10⁻³ m s⁻¹ to (0.35 ± 0.01) × 10⁻³ m s⁻¹, at 30 °C, mimicking crowded cellular environments. Notably, the protein Brownian velocity increased linearly with temperature. These results demonstrate the suitability of concentrated suspensions for modeling intracellular crowding and validate luminescent nanothermometry for protein Brownian motion studies. Furthermore, the observed linear relationship between the logarithm of the protein Brownian velocity and concentration indicates that EGFP motion is not primarily driven by diffusion, but more of a ballistic transport.