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Improving the heat transfer coefficient is crucial across various energy utilization processes for maintaining device safety and stability with high energy efficiency. However, in scenarios with limited heat capacity flow rates, increasing the thermal conductivity of encapsulated internal heat source (IHS) packaging can paradoxically impede heat transfer. Herein, we introduced a convective-meta thermal dispersion (CMTD) strategy applicable throughout the energy domain. By integrating low thermal conductivity materials into high thermal conductivity package structures, we disrupted tangential heat flow while preserving efficient radial heat transport. Through this approach, a notable reduction in tangential temperature within the fluid channel was achieved, effectively lowering the IHS temperature. Remarkably, this cooling mechanism does not need additional energy input, thermal property enhancements, or expanded heat transfer areas, which are often prerequisites in existing technologies. Moreover, spontaneous enhancement phenomena emerged under constrained heat transfer conditions, termed self-adaptive cooling enhancement. Our investigations revealed, under steady-state conditions, a maximum 24.5% decrease in IHS average temperature, while transient conditions exhibited a maximum 32.3% increase in heat transfer between the IHS and cooling fluid, validating the efficacy of the CMTD strategy. These findings offer a promising pathway for efficient thermal management in various thermal energy utilization fields with high power density such as nuclear fission and fusion and contributed to a deeper understanding of fundamental fluid-solid heat transfer mechanisms across the energy science.

The effects of chlorine (Cl) and zinc (Zn) co-doping on the electronic structure and optical properties of the zinc blende ({\gamma}) phase of copper iodide ({\gamma}-CuI) scintillator material are investigated by using first-principles density functional theory calculations. The band structure, density of states, dielectric function, absorption coefficients, and reflectivity were analyzed before and after doping. Results show co-doping significantly modifies the band structure, reduces the band gap, and generates impurity energy levels. Cl doping enhances absorption in the high energy region while reducing visible light absorption. Zn doping induces a redshift in absorption and n-type conductivity at high concentrations. With suitable co-doping ratios, the absorption coefficient and reflectivity of {\gamma}-CuI can be optimized in the visible range to improve scintillation light yield. The calculations provide guidance for co-doping {\gamma}-CuI scintillators to achieve superior detection performance. The n-type conductivity also makes doped {\gamma}-CuI promising for optoelectronic applications.

Thermal metamaterial represents a groundbreaking approach to control heat conduction, and, as a crucial component, thermal invisibility is of utmost importance for heat management. Despite the flourishing development of thermal invisibility schemes, they still face two limitations in practical applications. First, objects are typically completely enclosed in traditional cloaks, making them difficult to use and unsuitable for objects with heat sources. Second, although some theoretical proposals have been put forth to change the thermal conductivity of materials to achieve dynamic invisibility, their designs are complex and rigid, making them unsuitable for large-scale use in real three-dimensional spaces. Here, we propose a concept of a thermal dome to achieve three-dimensional invisibility. Our scheme includes an open functional area, greatly enhancing its usability and applicability. It features a reconfigurable structure, constructed with simple isotropic natural materials, making it suitable for dynamic requirements. The performance of our reconfigurable thermal dome has been confirmed through simulations and experiments, consistent with the theory. The introduction of this concept can greatly advance the development of thermal invisibility technology from theory to engineering and provide inspiration for other physical domains, such as direct current electric fields and magnetic fields.

Diffusion driven by temperature or concentration gradients is a fundamental mechanism of energy and mass transport, which inherently differs from wave propagation in both physical foundations and application prospects. Compared with conventional schemes, metamaterials provide an unprecedented potential for governing diffusion processes, based on emerging theories like the transformation and the scattering cancellation theory, which enormously expanded the original concepts and suggest innovative metamaterial-based devices. We hereby use the term "diffusionics" to generalize these remarkable achievements in various energy (e.g., heat) and mass (e.g., particles and plasmas) diffusion systems. For clarity, we categorize the numerous studies appeared during the last decade by diffusion field (i.e., heat, particles, and plasmas) and discuss them from three different perspectives: the theoretical perspective, to detail how the transformation principle is applied to each diffusion field; the application perspective, to introduce various intriguing metamaterial-based devices, such as cloaks and radiative coolers; and the physics perspective, to connect with concepts of recent concern, such as non-Hermitian topology, nonreciprocal transport, and spatiotemporal modulation. We also discuss the possibility of controlling diffusion processes beyond metamaterials. Finally, we point out several future directions for diffusion metamaterial research, including the integration with artificial intelligence and topology concepts., Comment: This review article has been published in Reviews of Modern Physics, volume 96, 015002 (2024)

The Stirling engine, which possesses external combustion characteristics, a simple structure, and high theoretical thermal efficiency, has excellent potential for utilizing finite waste heat and cold resources. However, practical applications of this technology suffered from thermal inefficiency due to the discontinuity and instability of waste resources. Despite advances in energy storage technology, temperature variations in the heat-exchanging fluids at the hot and cold ends of the Stirling engine remained significant obstacles. In this work, convective meta-thermal concentration (CMTC) was introduced between the heating (cooling) fluids and the hot (cold) end of the Stirling engine, employing alternating isotropic materials with high and low thermal conductivities. It was demonstrated that CMTC effectively enhanced the temperature difference between the hot and cold ends, leading to a remarkable improvement in Stirling engine efficiency. Particularly, when the Stirling engine efficiency tended to zero due to the limited availability of waste heat and cold resources, CMTC overcame this limitation, surpassing existing optimization technology. Further analysis under various operating conditions showed that CMTC achieved a significant thermal efficiency improvement of up to 1460%. This work expanded the application of thermal metamaterials to heat engine systems, offering an exciting avenue for sustainable energy utilization.

Muon radiography is an innovative and non-destructive technique for internal density structure imaging, based on measuring the attenuation of cosmic-ray muons after they penetrate the target. Due to the strong penetration ability of muons, the detection range of muon radiography can reach the order of hundreds of meters or even kilometers. Using a portable muon detector composed of plastic scintillators and silicon photomultipliers, we performed a short-duration(1h) flux scanning experiment of the overburden above the platform and tunnel of the Xiaoying West Road subway station under construction. With the observation direction facing up, the detector is placed on the north side of the track and moved eastward from the platform section inside the station to the tunnel section. The scanning length is 264m and a total of 21 locations are observed. By comparing the observed and predicted values of the muon survival ratio at different locations, the experiment accurately detects the jump in thickness at the interface of the platform section and tunnel section. Furthermore, unknown anomalies caused by random placed light brick piles and side passage mouth above the observation locations are detected and confirmed later. This experiment verifies the feasibility of using natural muons to quickly detect abnormal structures of the overburden of tunnel, and shows that muon radiography has broad application prospects in tunnel safety and other similar aspects., Comment: 30 pages, 10 figures

Thermal metamaterials provide rich control of heat transport which is becoming the foundations of cutting-edge applications ranging from chip cooling to biomedical. However, due to the fundamental laws of physics, the manipulation of heat is much constrained in conventional thermal metamaterials where effective heat conduction with Onsager reciprocity dominates. Here, through the inclusion of thermal convection and breaking the Onsager reciprocity, we unveil a regime in thermal metamaterials and transformation thermotics that goes beyond effective heat conduction. By designing a liquid-solid hybrid thermal metamaterial, we demonstrate a continuous switch from thermal cloaking to thermal concentration in one device with external tuning. Underlying such a switch is a topology transition in the virtual space of the thermotic transformation which is achieved by tuning the liquid flow via external control. These discoveries illustrate the extraordinary heat transport in complex multi-component thermal metamaterials and pave the way toward an unprecedented regime of heat manipulation.

Black holes are one of the most intriguing predictions of general relativity. So far, metadevices have enabled analogous black holes to trap light or sound in laboratory spacetime. However, trapping heat in a conductive ambient is still challenging because diffusive behaviors are directionless. Inspired by black holes, we construct graded heat-conduction metadevices to achieve thermal trapping, resorting to the imitated advection produced by graded thermal conductivities rather than the trivial solution of using insulation materials to confine thermal diffusion. We experimentally demonstrate thermal trapping for guiding hot spots to diffuse towards the center. Graded heat-conduction metadevices have advantages in energy-efficient thermal regulation because the imitated advection has a similar temperature field effect to the realistic advection that is usually driven by external energy sources. These results also provide insights into correlating transformation thermotics with other disciplines such as cosmology for emerging heat control schemes.

Topological polar vortices that are the electric analogues of magnetic objects, present great potential in applications of future nanoelectronics due to their nanometer size, anomalous dielectric response, and chirality. To enable the functionalities, it is prerequisite to manipulate the polar states and chirality by using external stimuli. Here, we probe the evolutions of polar state and chirality of polar vortices in PbTiO3/SrTiO3 superlattices under electric field by using atomically resolved in situ scanning transmission electron microscopy and phase-field simulations. We find that the adjacent clockwise and counterclockwise vortex usually have opposite chirality. The phase-field simulations suggest that the rotation reversal or axial polarization switching can lead to the chirality change. Guided by which, we experimentally validate that the vortex rotation direction can be changed by applying and subsequently removing of electric fields, offering a potential strategy to manipulate the vortex chirality. The revealed details of dynamic behavior for individual polar vortices at atomic scale and the proposed strategy for chirality manipulation provide fundamentals for future device applications.

In strong-field physics experiments with intense lasers, it is of paramount importance to single-shot diagnose the temporal contrast between laser pulse peak and its noise pedestal. This allows fast optimization of pulse contrast and meaningful comparison with theory for each pulse shot, and it can help new outcomes from clean laser-plasma interactions. Thus far, high contrast ratios up to ~10^10, required by present petawatt (PW) class lasers, have been accessible in both generation and single-shot characterization. However, ultrahigh contrast ~10^13, required by the planned 200-PW lasers, challenges intense laser technology and remains an open question. This paper reports on the first demonstration of such an ultrahigh-contrast measurement by adapting single-shot cross-correlator (SSCC). We introduce an ultrafast method that enables to determine the SSCC detection limit. Our strategy mimics the test laser having known ultrahigh contrast in the measurement frame of time-to-space mapping. The ultimate contrast-measurement limit of 10^13 is achieved, which corresponds to the highest pulse intensity set by SSCC damage threshold and the lowest noise pedestal set by single-photon detection. As a consequence, photon noise in the detection is observed and increases as the noise pedestal reduces. The demonstrated measurement ability at the photon noise limit is applied to a high-contrast laser system based on second-harmonic generation and optical parametric chirped-pulse amplification, suggesting accessible of ultrahigh contrast pulses., Comment: 12 pages, 4 figures