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In this manuscript, we present a comprehensive theoretical study on the observation of ultrastrong photon–phonon coupling in an all-perovskite Mie metasurface. In a metasurface comprising micro-cubes made of perovskite MAPbI 3 , we achieved an impressive Rabi splitting as large as 90% of the theoretical maximum. To elucidate the underlying mechanisms responsible for the observed ultrastrong coupling, we employed multipole decomposition analyses, which proved to be highly effective in distinguishing the relevant spectral peaks associated with the Rabi splitting. Our results demonstrate the potential of all-perovskite Mie metasurfaces as a platform for achieving unprecedented levels of light–matter interaction, with broad implications across multiple disciplines, including quantum optics, optoelectronics, and beyond.

Grounded in conservation of resources theory, this study investigated the relationship between customer mistreatment and organizational citizenship behavior by examining the mediating mechanism of depression in the workplace and the moderating role of emotional intelligence. Korean service employees ( N = 319) completed a survey at two time points spaced 3 weeks apart. We found that customer mistreatment diminished employees' organizational citizenship behavior through their sense of depression in the workplace. The results show that the positive relationship between customer mistreatment and depression in the workplace was weaker when employees had high emotional intelligence. The negative impact of customer mistreatment on organizational citizenship behavior was less pronounced for participants with high (vs. low) emotional intelligence. Theoretical and practical implications are discussed.

As the global economic situation deteriorates due to the prolonged COVID-19 pandemic, the business environment is plagued by uncertainty and risk. To address this, many organizations have sought to optimize efficiency, especially by downsizing and restructuring, to reduce costs. This causes anxiety among employees, who worry about whether they will be fired. We hypothesize that such job insecurity increases knowledge-hiding behavior by employees, and we investigate the mechanism underlying such a negative effect. In addition, we attempt to capture the boundary conditions of how to reduce the adverse effects of job insecurity, focusing on the role of coaching leadership. Using three-wave time-lagged cohort-study data from 346 Korean workers, we empirically found that employees who perceive job insecurity are less likely to feel organizational identification, leading to increased knowledge-hiding behavior. This study also demonstrated that coaching leadership operates as a boundary condition which buffers the negative influence of job insecurity on organizational identification. Theoretical and practical implications are discussed.

Electromagnetic absorbers based on ultra-thin metallic film are desirable for many applications such as plasmonics, metamaterials, and long-wavelength detectors. A metallic film will achieve a maximum 50% of electromagnetic wave absorption, frequency independent, at a thickness defined by its conductivity, typically in the sub-Angstrom range for good metals if bulk conductivity is maintained throughout. This makes it extremely difficult to obtain substantial absorption from thin metal films, in contrast to 2D materials such as graphene. Luckily, however, from a practical point of view, metal conductivity is drastically reduced as the film becomes sub-100 nm, to make it a race between the thinnest possible metal thickness experimentally achievable vs the conductivity reduction. Here, we demonstrate a near-50% absorption at a gold film thickness of 6.5 nm, with conductivity much reduced from the bulk value, down to the range of 10 6 Siemens per meter. Studying the effect of the substrate thickness, we found that the common cover glass, with its thickness much smaller than the wavelength, achieves symmetric absorption of 44%, implying that a pseudo-free-standing limit is achieved. Our work may find applications in infrared sensing as in bolometers and biomedical sensing using microwaves.

Background This study investigates the impact of customer incivility on employee burnout and work-family conflict, examining the moderating role of ethical leadership in these relationships within the service industry. By integrating the Conservation of Resources theory and Role Theory, we seek to provide a more comprehensive understanding of how negative customer interactions affect employee well-being beyond the immediate work setting. Methods We conducted a two-wave, time-lagged survey among 586 full-time service sector employees in South Korea. The data were analyzed using confirmatory factor analysis and hierarchical regression to test the hypothesized relationships between customer incivility, burnout, work-family conflict, and ethical leadership. Results Our results reveal a positive relationship between customer incivility and work-family conflict, which is mediated by burnout. Furthermore, we found that ethical leadership moderates the relationship between customer incivility and burnout, such that the positive relationship is weaker when ethical leadership is high. Conclusion By integrating Conservation of Resources theory and Role Theory, this study provides a comprehensive understanding of how negative customer interactions affect employee well-being beyond the immediate work setting. The results highlight the spillover effects of customer incivility on employees’ personal lives and the importance of ethical leadership in mitigating these effects. This research offers valuable insights for developing targeted interventions to enhance employee well-being, work-family balance, and organizational effectiveness in service industries.

With recent advances in nanofabrication technology, various metallic gap structures with gap widths reaching a few to sub-nanometer, and even ‘zero-nanometer’, have been realized. At such regime, metallic gaps not only exhibit strong electromagnetic field confinement and enhancement, but also incorporate various quantum phenomena in a macroscopic scale, finding applications in ultrasensitive detection using nanosystems, enhancement of light–matter interactions in low-dimensional materials, and ultralow-power manipulation of electromagnetic waves, etc. Therefore, moving beyond nanometer to ‘zero-nanometer’ can greatly diversify applications of metallic gaps and may open the field of dynamic ‘gaptronics.’ In this paper, an overview is given on wafer-scale metallic gap structures down to zero-nanometer gap width limit. Theoretical description of metallic gaps from sub-10 to zero-nanometer limit, various wafer-scale fabrication methods and their applications are presented. With such versatility and broadband applicability spanning visible to terahertz and even microwaves, the field of ‘gaptronics’ can be a central building block for photochemistry, quantum optical devices, and 5/6G communications.

Metallic nanogaps are being widely used for sensing applications, owing to their ability to confine and enhance electromagnetic field within the hot spots. Since the enhanced field does not confine itself perfectly within the gap, however, fringe fields well away from the gap are of potential use as well in real systems. Here, we extend the concept of near field absorption enhancement by quantitatively analyzing terahertz absorption behavior of water molecules outside the hot spots of sub-20 nm-wide, ∼100 μm-long nanotrenches. Contrary to point-gaps which show negligible field enhancement at distances larger than the gap width, our extended nanogap act as a line source, incorporating significant amount of absorption enhancement at much longer distances. We observe absorption enhancement factors of up to 3600 on top of a 5 nm-wide gap, and still well over 300 at 15 nm away. The finding is well supported by theoretical analyses including modal expansion calculations, Kirchhoff integral formalism and antenna theory. Our results provide means to quantitatively analyze light-matter interactions beyond the hot spot picture and enable application of nanogaps for sensitive surface analyses of various material systems.

Various material properties change considerably when material is thinned down to nanometer thicknesses. Accordingly, researchers have been trying to obtain homogeneous thin films with nanometer thickness but depositing homogeneous few nanometers thick gold film is challenging as it tends to form islands rather than homogenous film. Recently, studies have revealed that treating the substrate with an organic buffer, (3-mercaptopropyl) trimethoxysilane (MPTMS) enables deposition of ultra-thin gold film having thickness as low as 5 nm. Different aspects of MPTMS treatment for ultra-thin gold films like its effect on the structure and optical properties at visible wavelengths have been investigated. However, the effect of the MPTMS treatment on electrical conductivity of ultra-thin gold film at terahertz frequency remains unexplored. Here, we measure the complex conductivity of nanometer-thick gold films deposited onto an MPTMS-coated silicon substrate using terahertz time-domain spectroscopy. Following the MPTMS treatment of the substrate, the conductivity of the films was found to increase compared to those deposited onto uncoated substrate for gold films having the thickness less than 11 nm. We observed 5-fold enhancement in the conductivity for a 7 nm-thick gold film. We also demonstrate the fabrication of nanoslot-antenna arrays in 8.2-nm-thick gold films. The nanoslot-antenna with MPTMS coating has resonance at around 0.5 THz with an electric field enhancement of 44, whereas the nanoslot-antenna without MPTMS coating does not show resonant properties. Our results demonstrate that gold films deposited onto MPTMS-coated silicon substrates are promising advanced materials for fabricating ultra-thin terahertz plasmonic devices.

A metallic nano-trench is a unique optical structure capable of ultrasensitive detection of molecules, active modulation as well as potential electrochemical applications. Recently, wet-etching the dielectrics of metal–insulator–metal structures has emerged as a reliable method of creating optically active metallic nano-trenches with a gap width of 10 nm or less, opening a new venue for studying the dynamics of nanoconfined molecules. Yet, the high surface tension of water in the process of drying leaves the nano-trenches vulnerable to collapsing, limiting the achievable width to no less than 5 nm. In this work, we overcome the technical limit and realize metallic nano-trenches with widths as small as 1.5 nm. The critical point drying technique significantly alleviates the stress applied to the gap in the drying process, keeping the ultra-narrow gap from collapsing. Terahertz spectroscopy of the trenches clearly reveals the signature of successful wet etching of the dielectrics without apparent damage to the gap. We expect that our work will enable various optical and electrochemical studies at a few-molecules-thick level.

Slot antennas have been exploited as important building blocks of optical magnetism because their radiations are invoked by the magnetic fields along the axes, as vectorial Babinet principle predicts. However, optical magnetism of a few-nanometer-width slit, for which fascinating applications are found due to the colossal field enhancement but Babinet principle fails due to the nonnegligible thickness, has not been investigated. In this paper, we demonstrated that the magnetic field plays a dominant role in light transmission through a 5-nm slit on a 150-nm-thick gold film. The 5-nm slit was fabricated by atomic layer lithography, and the transmission was investigated for various incident angles by experiment and simulation at 785-nm wavelength. We found that, due to the deep subwavelength gap width, the transmission has the same incident angle dependence as the tangential magnetic field on the metal surface and this magnetic nature of a nanogap holds up to ~100-nm width. Our analysis establishes conditions for nanogap optical magnetism and suggests new possibilities in realizing magnetic-field-driven optical nonlinearities.