The coupling effects of surface plasmon resonance (SPR) from metamaterials induce variation in both the frequency and intensity of plasmonic modes. Here, we report an angular-dependent THz modulator with hybrid metal–graphene metastructures. The metastructures composed of the period gold split-rod arrays on top of a monolayer graphene, which show redshift modulation in the THz region with an increasing incident angle due to the strong out-of-plane magnetic flux introduced by the clockwise circular current at the oblique incidence. By utilizing graphene-based actively tunable conductor with ion-gel electrical gating, the THz transmission can be significantly modified. The modulation depth of the hybrid metal–graphene metastructure modulator can reach ~37.6% at 0.62 THz with a gate voltage of −3 V. The theoretical modeling of transmitted dependency on frequency and incident angle is demonstrated at different Fermi energies, which fits well with the experimental results. This hybrid device can offer a useful method for THz applications (such as angle sensors or angular-resolved spectroscopy), where angle-dependent modulation is needed.

具有非晶状热导率的固体材料在热能转换和热管理应用中备受青睐。因此，揭示晶体材料的非晶状热传导机理对于开发和设计低热导率材料至关重要。本文运用原子模拟方法揭示了萤石结构二元简单晶体Yb₃TaO₇的非晶状低热导率的物理机理。研究发现，萤石Yb₃TaO₇的低热导率主要是由O-Yb和O-Ta之间的原子间结合力相差较大引起的。这种相差较大的原子键可以极大地软化声子模式，从而抑制声子输运。振动模式分解显示，萤石Yb₃TaO₇中的大多数声子模式位于Ioffe-Regel极限以下，表现出强烈的扩散特征。萤石Yb₃TaO₇中绝大部分（>90%）的热流是通过扩散模式而不是传播模式传输的。因此，萤石Yb₃TaO₇中的热传导表现出独特的类非晶特性。同时发现，萤石Yb₃TaO₇中的光学声子模式在热传导中发挥着重要的作用。本文对于原子间结合力与低热导率之间关系的认识为开发和设计低热导率材料提供了新的思路。

Understanding the origin of ultralow lattice thermal conductivity (κL) in crystals is crucial for the development of advanced thermoelectric and thermal management materials. This study systematically investigates thermal transport mechanisms in perovskite CsPbBr3 crystals using a novel framework that integrates quartic anharmonicity-driven phonon spectral renormalization at finite temperatures with machine learning potential-driven molecular dynamics. In contrast to results from ground-state anharmonic lattice dynamics, our findings reveal that the ultralow κL in CsPbBr3 predominantly arises from particle-like phonon propagation rather than wave-like phonon coherence, due to anharmonic renormalization shifting most phonon modes from the Wigner limit into the propagation regime. Furthermore, the temperature-dependent quartic anharmonicity effectively promotes particle-like while limiting wave-like phonon transport channels, accurately reproducing the experimental ultralow κL of CsPbBr3 in magnitude and temperature dependence. This study not only resolves the discrepancy between measured and predicted κL in CsPbBr3 crystals but also reveals the dominant role of particle-like phonon propagation in flat ultralow κL, providing a revised physical picture for understanding anharmonic thermal transport and critical insights for regulating κL of materials through lattice anharmonicity.

Benefiting from a high quantum efficiency, low thermal emittance, and large absorption coefficient, In_xGa_1−xAs is an excellent group III–V compound for negative electron affinity (NEA) photocathodes. As the emission layer, In_xGa_1−xAs, where x = 0.15, has the optimal performance for detection in the near-infrared (NIR) region. Herein, an NEA In_0.15Ga_0.85As photocathode with Al_0.63Ga_0.37As as the buffer layer is designed in the form of a transmission mode module. The electronic band structures and optical properties of In_0.15Ga_0.85As and Al_0.63Ga_0.37As are calculated based on density functional theory. The time response characteristics of the In_0.15Ga_0.85As photocathode have been fully investigated by changing the photoelectron diffusion coefficient, the interface recombination velocity, and the thickness of the emission layer. Our results demonstrate that the response time of the In_0.15Ga_0.85As photocathode can be reduced to 6.1 ps with an incident wavelength of 1064 nm. The quantum efficiency of the In_0.15Ga_0.85As photocathode is simulated by taking into account multilayer optical thin film theory. The results indicate that a high quantum efficiency can be obtained by parameter optimization of the emission layer. This paper provides significant theoretical support for the applications of semiconductor photocathodes in the near-infrared region, especially for the study of ultrafast responses in the photoemission process.