Thin-film polycrystalline photovoltaics like CdTe possess high power-conversion efficiency, but still suffer from low open-circuit voltage $V_{OC}$. Grain boundaries are believed to reduce $V_{OC}$, yet a precise understanding of their impact on device performance is lacking. The authors derive analytic expressions for $V_{OC}$ in terms of grain-boundary and material parameters for various grain-boundary defect configurations, and verify their results against numerical simulations. Their insight should assist in optimizing the defect chemistry of grain boundaries and mitigating their impact on $V_{OC}$, on the way to a solar-powered future.

Metasurfaces offer versatile manipulation of light beams via low-loss, low-profile structures, but practical developments are impeded by heavy reliance on time-consuming full-wave simulations. In this study of $metagratings$, sparse periodic arrays of meta-atoms that can efficiently realize intricate field transformations, the authors present a detailed model based on capacitively loaded conducting wires. Perfect wide-angle beam splitters can be designed almost completely analytically, without the usual computational burden. The sensitivity of these metagratings to real-world imperfections is directly related to fundamental interference processes.

Although ion exchange is commonly used to strengthen oxide glasses, the products usually reach just a small fraction of their maximum theoretical strength, due to the so-called atomic network dilation anomaly. Based on molecular dynamics simulations, this study reveals that the dilation anomaly is topological in origin. Surprisingly, glasses exhibiting an optimal (isostatic) atomic topology are found to be free of this anomaly. These results establish topological nanoengineering as a promising route to designing ultrastrong glasses, with significant implications for industry—and your next mobile phone.

Lateral heterostructures of two-dimensional materials, featuring adjacent metallic and semiconducting regions, offer additional transistor concepts for logic. By means of precise multiscale simulations, the authors investigate various device designs based on monolayer MoS${}_2$ using $1T$ and $2H$ phases, and find that the proposed structures exhibit better intrinsic performance than CMOS technology. Promising figures of merit for digital logic, plus the possibility to avoid chemically doped regions, make monolayer-MoS${}_2$ devices interesting candidates for next-generation electronics.

The optical Kerr effect, in which a medium’s refractive index is affected by the intensity of the transmitted light, is exploited not only in conventional optics, but also in superconducting circuits. This article reports a Josephson-junction-based metamaterial with a widely tunable Kerr constant that can even change sign. Controlled by an external magnetic field, this material can speed up or slow down the phase velocity of light per the intensity of the propagating electromagnetic wave. Such an engineered medium could be used for phase matching in traveling-wave parametric amplifiers, or in superconducting hardware for encoding or reading out quantum information.

Atomic clocks based on coherent population trapping (CPT) are of great interest for portable applications, due to their high performance, low power requirements, and potential for miniaturization. Slow frequency drift, however, limits their holdover ability on long time scales. This study reports a CPT clock that minimizes long-term drift, with a fractional frequency stability of $3\times {10}^{-13}$ over the span of an hour—ten times as good as previous CPT clocks. After successful shrinking of the laser-cooling apparatus, this clock could see commercial use, as the atoms fall just a few millimeters during a typical probe period.

Metastable $ϵ$-gallium oxide is expected to have very good properties for high-power electronics, combining the large band gap and high breakdown field of $\beta$-Ga${}_2$O${}_3$ with a very high spontaneous polarization. Unfortunately, synthesizing $ϵ$-Ga${}_2$O${}_3$ is quite tricky, yet the authors have managed it. Introducing tin avoids the formation of volatile suboxides, which leadsto a widened growth window in which $ϵ$-gallium oxide can beformed. Furthermore, the growth mechanism that the authors revealcould be relevant for the growth of any binary oxide.

Magnetic sensing and imaging using ensembles of nitrogen-vacancy (N-$V$) centers in diamond recently have found application in disciplines as wide-ranging as condensed matter physics, biology, and paleomagnetism. However, distinguishing the signals from the four inequivalent N-$V$ orientations requires an external magnetic field, which can hinder the study of some magnetic samples. The authors present an $all-optical$ method to tease apart the signals at arbitrary bias fields, by exploiting the distribution of photoluminescence at the Fourier plane of a microscope. Their technique will help N-$V$-based magnetic sensing reach its full potential.

$p-n$ junctions in graphene on a ferroelectric substrate have been studied as a possible basis for electronic devices, but what about the impact of the piezoelectric effect? What happens to graphene’s properties when ferroelectric domain stripes of opposite polarization elongate or contract, depending on the polarity of an applied voltage? The authors find that the alternating piezodisplacement of domain surfaces can lead to stretching and separation of graphene at the steps between domains. This can cause a significant increase in graphene channel conductance in a field-effect transistor, and so provides a control mechanism for devices.

Detection and imaging using light at terahertz frequencies continues to be a topic of keen interest for numerous applications. Recent investigations have shown that stacks of natural Josephson junctions in cuprate superconductors are suitable emitters of THz radiation; now our attention turns to effective use of such a source. Using two setups, one featuring bolometric detection and the other heterodyne, the authors achieve results respectively comparable to those for time-domain spectroscopy and systems based on quantum cascade lasers. These findings indicate that their setups are in fact suitable for gas sensing in environmental monitoring.

It can be hard to find that perfect match—even, or perhaps especially, in quantum electronics. Microwave readout of highly Ohmic quantum devices, like superconducting qubits, necessitates impedance-matching circuits to maximize power transfer. $LC$ resonant circuits enjoy two major advantages over well-established coplanar transmission-line circuits: larger bandwidths (and thus shorter readout times), and drastically smaller on-chip footprints. With this in mind, the authors develop a compact $LC$ resonator operating at 3 GHz to bridge a load of ~15 k$\mathrm{\Omega }$ to a typical coaxial line at 50 $\mathrm{\Omega }$—match made.

Fast, accurate measurement of superconducting qubits demands approaching the quantum limit in amplifying weak microwave probe tones. An ideal amplifier would provide $nonreciprocal$ (high forward, negligible reverse) gain, protecting the qubit from noisy downstream measurements. The superconducting low-inductance undulatory galvanometer (SLUG) microwave amplifier provides highly directional gain and minimal backaction on the qubit, as the authors demonstrate by studying its performance in a circuit without microwave circulators or isolators. This elimination of bulky, magnetic nonreciprocal elements shows a way to scalable measurement of large multiqubit arrays.

In physics, similarities can crop up in the most unexpected places. This study, for example, exploits the striking analogy between single ions in microscopic moving traps and the loads moved by mechanical cranes. Though the systems are separated by many orders of magnitude in mass and shuttling distance, results and concepts may be translated from the microscopic domain to the macroscopic, and $vice$ $versa$. “Shortcuts to adiabaticity” techniques based on dynamical invariants of motion allow for fast, ultrarobust load control for unknown initial conditions for cranes, while the analysis of energy consumption for cranes can be translated to ion traps.

Despite the success of multimode devices for high information throughput, most state-of-the-art optical switching employs single-mode operation. This study demonstrates the switching of random light waves via the collective manipulation of multimodes. From supersymmetric building blocks that form parity-reversed contacts, binary switching and many-valued logic are achieved with lossless transfer of arbitrary wave fronts. This result paves the way for high-bandwidth data processing and “fuzzy photonics”, an approach to ultrafast artificial intelligence.

Very high layered crystallinity is achieved in some alkyl-substituted organic semiconductors, allowing high-performance organic thin-film transistors (OTFTs). The authors observe that nonlinear device characteristics depend on the number of layers, for OTFTs based on large-area single-crystalline films of Ph-BTBT-Cn. This nonlinearity is caused by tunneling-based access resistance across layers of alkyl chains, which is the origin of the wide device-to-device variation in mobility seen in single-crystalline OTFTs. With this understanding, since these insulating chains can be tuned by length, they are a point for device optimization.

The authors introduce a model for field-effect-transistors (FETs) that closes the gap between detailed charge-transport simulations and highly simplified equivalent-circuit models. It is flexible, fast, and easy to use, yielding physically meaningful parameters and allowing the complex scaling behavior of nanoscale transistors to be more easily incorporated into circuit simulations. Its application reveals, importantly, that the static and dynamic characteristics of a FET at very small device dimensions are strongly affected by nonlinear contact resistance.

Glass fractures according to a probabilistic law that requires multiple, delicate experiments for characterization. As it turns out, the patterns created during femtosecond laser exposure offer rich insight about the failure behavior of brittle materials. These patterns of random length alternate between being self-organized and highly disorganized, and this intermittency can be correlated to the statistical law governing the fracture. This fast, straightforward, microscopic method opens opportunities for rapid diagnosis in, for instance, quality control of glass in consumer electronics, which is currently difficult to implement.

The ability to generate states of light with specific quantum correlations is very important in quantum communication and computation. While this ability has been realized in bulk optics, most approaches implemented so far are not suitable for the integrated photonic circuits that are expected to revolutionize quantum photonics in the near future. This work shows that, by using the path-encoding representation, one can generate entangled Greenberger-Horne-Zeilinger states in an integrated device. This approach is scalable and compatible with several platforms, from laser-written devices to silicon photonics.

Single photons are expected to play a key role in tomorrow’s quantum communication networks, owing to the robustness of photonic quantum states and their ability to travel long distances. This study demonstrates a generator that can give individual photons a desired “shape”, which can increase their efficiency when used in a quantum network. Here the emission of an artificial atom (a superconducting circuit) is controlled by manipulating quantum vacuum fluctuations on nanosecond timescales. This tunable coupling principle could also see use in controlling quantum interactions in a variety of applications beyond single-photon generation.

Alnico alloy is a very promising candidate for rare-earth-free, high-performance permanent magnets, especially for high-temperature and levitation applications—including motors for electric vehicles. Engineering better magnets, and motors, is stymied by a lack of knowledge of alnico’s nanoscale structure. Using advanced simulation methods, this study investigates the dependence of chemical composition and ordering of magnetic and matrix phases of alnico on annealing temperature. A surprising phase forms when the system is annealed at low temperatures, offering a possible route to improving alnico’s performance.

Pump-probe electron energy-loss spectroscopy is a promising method for studying electron dynamics and photoexcited chemistry in real time. Existing instruments using low-energy electrons cannot achieve adequate temporal resolution, and while bright high-energy electron beams could, their energy resolution is orders of magnitude worse. The authors propose a reference-beam concept, supported by comprehensive system design and numerical modeling, that can completely bypass these challenges. Their work points the way to mapping the atomic world on fundamental time, length, and energy scales.

A dielectric material can store electrical energy via the fast response of its polarization under an applied electric field. Unfortunately, environmentally friendly Pb-free ferroelectrics show high hysteresis loss, low permittivity, and a narrow applicable temperature range, which limit their performance in applications. This work describes the physics of the unusual ferroelectric glass-glass transitions in a particular Pb-free ceramic that yield tiny thermal hysteresis, a large dielectric constant, and good polarization over a wide temperature range. This understanding should help to advance dielectric-based technology for energy storage.

The mixing of propagating and evanescent light waves to form images in the near field of an emitting or reflecting surface is crucial to developing new imaging techniques. The lack of a remote superresolving detection scheme, however, has left this area largely unexplored. In this study, a remote structured-illumination technique is used to inspect imaging in the near field for THz frequencies (wavelengths of 0.1—1 mm). The authors demonstrate a simple mechanical scheme to overcome the diffraction limit, achieving a resolution better than 1/10 of the wavelength, which may allow the development of inexpensive, superresolved THz imagers for $e.g.$ security applications.

Thermophotovoltaic (TPV) systems could be very attractive for energy efficiency, as they allow the harvesting of radiative waste heat as electricity. The authors describe an efficient TPV generator whose spectrum of radiative thermal power is frequency-selective and exceeds the Planckian limit. Their device does not require a vacuum gap between the hot and cold parts of the system, and can be handily realized with existing nanofabrication methods. Thus this work shows the way to efficient TPV generators that are quite practical for application.

Heat-assisted magnetic recording (HAMR) may be the most promising technology for tomorrow’s ultrahigh-density data storage, but magnetic noise at high temperatures significantly limits the achievable storage capacity. The choice of recording medium is crucial to realizing the full potential of HAMR. This extensive study reveals how introducing an Fe-Rh layer into exchange-coupled material grains can reduce noise. By elucidating the physics behind the noise reduction and highlighting important design guidelines, this work is expected to have significant impact on future hard-disk-drive applications.

Being able to grow semiconducting nanowires, each with an embedded quantum dot, paves the way to practical single-photon sources. The inherently small size of these sources, however, hampers their emission efficiency and coupling to external collection optics ($e.g.$ optical fibers). To address this problem, the authors demonstrate a simple and robust way to fabricate a photonic-fiber shell around a nanowire to enhance its emission properties, and elucidate the photophysical mechanisms behind the enhancement. This bottom-up fabrication technique is a substantial step toward more efficient quantum light sources.

Developing technology to exploit the “THz window” of the electromagnetic spectrum continues to be a major research theme. Stacks of intrinsic Josephson junctions in a cuprate superconductor are a good source of THz photons; with them, one can even imagine a THz laser on a chip. To better understand the purity of this radiation, the authors study the phenomenon of self-mixing, in which the nonlinearity of the Josephson elements leads to two or more nearby THz emission peaks producing signals at the difference frequencies. These results are helpful for synchronizing thousands of Josephson junctions, and may offer a simple method for evaluating the coherence of their THz emission.

Optical scattering at the nanoscale continues to lead to physical insights and various applications, including optical antennas and metamaterials and metasurfaces. The differential light-scattering cross section of a $single$ nanostructure, however, has remained elusive, despite being the fundamental parameter for characterizing scattering properties. This article presents quantitative, isolated measurements of the differential cross section and its far-field distribution for a lone gold nanorod. Simulations and modeling are in excellent agreement with the results, showing the phenomena and mechanisms that must be taken into account when engineering devices.

Exploring collective quantum phenomena is aided by model systems of cold gases of (quasi)particles, such as spatially indirect excitons in a semiconductor—but a proper control system is needed. This study provides a technique to manipulate the confinement energy of indirect excitons, relying only on dipolar coupling to the evanescent electric field inside a field-effect device, with no need for impedance matching. A microscopic trap offers control with nanosecond precision at subkelvin temperatures, without incidental heating, for direct application in studying excitonic Bose-Einstein condensates, and in tuning excitonic transition energies in semiconductor quantum optics.

Thin-film polycrystalline photovoltaics like CdTe possess high power-conversion efficiency, but still suffer from low open-circuit voltage $V_{OC}$. Grain boundaries are believed to reduce $V_{OC}$, yet a precise understanding of their impact on device performance is lacking. The authors derive analytic expressions for $V_{OC}$ in terms of grain-boundary and material parameters for various grain-boundary defect configurations, and verify their results against numerical simulations. Their insight should assist in optimizing the defect chemistry of grain boundaries and mitigating their impact on $V_{OC}$, on the way to a solar-powered future.

In view of future spintronic and spin-optronic devices, such as spin light-emitting diodes and spin lasers, it is important to understand the dependence of electrical spin injection on bias in bipolar devices based on GaAs. Focusing on the efficiency of Co-Fe-B/MgO spin injectors, the authors investigate the influence of the MgO growth process on this bias dependence, using MgO tunnel barriers fabricated by different techniques. The bias dependence of spin injection efficiency, and the compromise between high intensity and high circular polarization of electroluminescence, depend strongly on the characteristics of the interface, which can be engineered by the growth process.

In superconducting spintronics, ferromagnetic \pi Josephson junctions are attractive for qubits, cryogenic memory, and phase shifters in logic circuits, offering reduced cell size and superior coherence and scalability. This study demonstrates such junctions based on niobium nitride, which can be grown epitaxially on MgO and is compatible with existing hardware. Its results provide physical insight into superconducting spintronics, as well as an interesting component for applications in quantum information processing.

In the blossoming field of spin caloritronics, the coupling of spin to charge and thermal currents is exploited to raise the efficiency of nanoscale devices for on-chip conversion of heat to electricity, for example. The authors’ analysis shows that using magnetic leads in a structure with overlapping graphene nanoribbons allows the optimization of its charge- and spin-dependent thermoelectric properties. Outstanding spin- and charge-based figures of merit are identified, indicating the great potential of such devices for energy harvesting at the nanoscale.

In quantum information processing, the Josephson parametric amplifier (JPA) has become a crucial tool for fast, high-fidelity readout of superconducting qubits, and for the generation of squeezed microwave radiation. However, research groups worldwide have reported unexpected nonidealities in these devices, leading to poorer than anticipated performance. Using numerical simulations complemented by experiments, the authors pinpoint oft-neglected higher-order circuit nonlinearities as the main source of these nonidealities, and provide simple, concrete steps to improve JPA performance.

Spin pumping is recognized as a powerful means to create spin current from the precession of magnetization. Taking a hint from spin caloritronics, the authors demonstrate an unconventional mechanism of dynamical spin injection, based on the heating due to ferromagnetic resonance. Using a high-performance ferromagnetic alloy for the thermal process, efficient dynamical spin injection is achieved. This ingenuity opens another avenue for wireless spintronic devices.

Methods for generating acoustic fields, as in ultrasound scans, generally rely on a linear process within the transducer. In this study, an acoustic signal is generated using the $nonlinear$ effects observed in granular chains via propagation of solitary waves. An analytical model is developed to simulate the behavior of a granular chain attached to an impedance-matching layer (which helps to deposit the ultrasonic energy into biological tissue). A prototype device with a chain of aluminum spheres and a vitreous-carbon matching layer demonstrates the feasibility of such systems for biomedical applications.

Chances are, you’re reading this text on an LCD screen—and your next screen could be based on what you are about to read. This article reports a display technology with the same cell structure as in the in-plane-switching LCDs currently mass produced, yet based on very different physics. The authors study the dynamics of the flexoelectric effect in a hybrid liquid-crystal geometry, for which crystal orientation depends on the polarity of an applied voltage (positive polarity yielding counterclockwise rotation). Here turn-on and -off times are inversely proportional to the voltage, and are potentially less than a millisecond.

Vibration shielding is a core concept in applications including precision manufacturing, vehicle design, and interfloor noise reduction in architecture. Blocking broad ranges of extremely low frequencies remains a challenging, unresolved problem. The authors present an elastic metamaterial based on the dual ideas of $rotation$ $softening$ and $shear$ $stiffening$, to shield against flexural waves from 235 to 4520 Hz, covering nearly the entire range of conventional frequencies. These small, lightweight, mass-beam-plate structures could provide many solutions in acoustic engineering.

When making a quantum measurement, one must be careful not to disturb the system. Nonreciprocal elements called isolators allow microwave signals to propagate in one direction but not the reverse, and so can mitigate disturbance, but commercial isolators require strong permanent magnets that cannot be placed close to superconducting amplifiers or qubits. To this end, the authors demonstrate a microwave isolator with directionality provided by a strong, traveling “pump” wave. Its simple construction and large bandwidth afford this isolator integrability with existing superconducting quantum hardware.

On-board detection of an object’s rotation is important for $e.g.$ inertial navigation, geophysics, and testing general relativity. The authors point out that a gas of molecules with permanent dipole moments, such as CH${}_3$F or NH${}_3$, can act as a detector when an electric field turns around it. In analogy to an NMR experiment, an rf pulse knocks the dipole moment into precession, and any rotation of the external field induces a shift in the precessional frequency. Though there is room for improvement, this approach could be rather interesting, particularly for environments where using magnetism would be problematic.

Metasurfaces offer versatile manipulation of light beams via low-loss, low-profile structures, but practical developments are impeded by heavy reliance on time-consuming full-wave simulations. In this study of $metagratings$, sparse periodic arrays of meta-atoms that can efficiently realize intricate field transformations, the authors present a detailed model based on capacitively loaded conducting wires. Perfect wide-angle beam splitters can be designed almost completely analytically, without the usual computational burden. The sensitivity of these metagratings to real-world imperfections is directly related to fundamental interference processes.

Improving the dimensionless figure of merit $ZT$ is perhaps the most important topic in thermoelectric energy conversion. $ZT$ depends oppositely on the electrical and thermal conductivities of a material, though, and they both depend on the mobility of electrons. This interdependence makes simultaneous optimization of both conductivities a real challenge. Spin caloritronics may offer a way forward: The authors propose a device to exploit the spin Nernst and inverse spin Hall effects, to break the interdependence of the conductivities and offer alternate strategies for waste-heat scavenging.

Applications in nanophotonics and optical quantum information processing often require just one photon at a time. Although typical single-photon emitters rely on electronic states localized at the nanometer scale, the authors find that carbon nanotubes over 2 $\mu$m long exhibit photon antibunching at room temperature. Monte Carlo simulations and first-passage theory reveal that high-purity single-photon emission from this system is possible in principle, by means of efficient exciton-exciton annihilation. These results point to design strategies for single-photon sources, and provide important insight into excitonic processes in carbon nanotubes.

Although ion exchange is commonly used to strengthen oxide glasses, the products usually reach just a small fraction of their maximum theoretical strength, due to the so-called atomic network dilation anomaly. Based on molecular dynamics simulations, this study reveals that the dilation anomaly is topological in origin. Surprisingly, glasses exhibiting an optimal (isostatic) atomic topology are found to be free of this anomaly. These results establish topological nanoengineering as a promising route to designing ultrastrong glasses, with significant implications for industry—and your next mobile phone.

Resistive switching in transition-metal oxides has garnered much attention for emerging applications such as memristive nonvolatile memory and neuromorphic computing, yet the effect of filament formation in the metal-insulator transition (MIT) in Mott/Peierls materials has not. The authors study the resistive-switching properties of VO${}_2$ and V${}_2$O${}_3$ nanodevices, observing that multiple MITs appear when a high enough voltage is applied. The hysteresis of these MITs provides an extra mechanism for memory applications, which could offer additional functionalities in memristive hardware.

Although scattering-type scanning near-field infrared microscopy can provide access to key parameters of nanomaterials, presently it is performed with unoptimized gold-coated cantilever probes, mainly due to their commercial availability. This work demonstrates that heavily doped germanium, with a midinfrared plasma frequency, is also a good choice for such probes. The peculiarities of IR plasmonic resonances of doped semiconductor nanostructures are highlighted with the aid of multiple-scattering models. This development in coating-free monolithic tips for scanning-probe microscopy could facilitate a lot of nanotechnology research, particularly in plasmonics and photonics.

Perfecting the complex morphology of bulk heterojunction blends in organic solar cells is key to obtaining the rapid, long-range charge transport needed for efficient devices. Quantifying these morphological details and their impact on transport has been difficult, though. Combining realistic model forms with kinetic Monte Carlo simulations of transport, this computational study investigates how the winding nature of the transport pathways affects carrier mobility in blended materials. The results are used to provide detailed, physical recommendations for an experimental measurement protocol to accelerate material and device optimization.

In the cutting of metal, central to countless manufacturing processes, the well-known and counterintuitive fact is that soft metals are much more difficult to cut than hard ones; very large forces are involved, and a poor surface finish is obtained. Grain-scale $in$ $situ$ imaging reveals that when soft metal is cut, laminar flow is inherently unstable and material is removed instead via $sinuous$ flow, a mesoscale mode involving repeated folding, with significant vortexlike components. These observations suggest control strategies with important performance benefits for manufacturing, as well as a need to reexamine the foundations of cutting and large-strain deformation at surfaces.

Random number generation is critical for many emerging computing schemes, but the associated energy consumption and circuit area are major bottlenecks. This study exploits the stochastic behavior of superparamagnetic tunnel junctions, magnetic nanodevices that, due solely to thermal noise, will switch randomly between two well-defined states. These tunnel junctions can produce high-quality, truly random bit streams, with an energy efficiency that is orders of magnitude better than the state of the art. The authors furthermore develop an example that highlights the utility of superparamagnetic random number generation for low-energy probabilistic computing.

Understanding transient phases that evolve during solidification can be critical to phase selection and the resulting microstructure of an alloy. However, the nature of high-temperature metastable phases makes them difficult to study with conventional techniques. The authors combine a tunnel-diode oscillator, electrostatic levitator, and x-ray diffraction for contactless precision measurement of magnetic transitions during the freezing of Fe-B, an industrially important material. This technique will prove invaluable for studying high-temperature magnetism in challenging systems.

Lateral heterostructures of two-dimensional materials, featuring adjacent metallic and semiconducting regions, offer additional transistor concepts for logic. By means of precise multiscale simulations, the authors investigate various device designs based on monolayer MoS${}_2$ using $1T$ and $2H$ phases, and find that the proposed structures exhibit better intrinsic performance than CMOS technology. Promising figures of merit for digital logic, plus the possibility to avoid chemically doped regions, make monolayer-MoS${}_2$ devices interesting candidates for next-generation electronics.

The waveguide-fed metasurface is an emerging concept for beam forming and wave-front shaping, with applications that include satellite and terrestrial communication, radar, rf imaging, and wireless power transfer. The present work provides in-depth analysis of metasurface antenna operation. A set of simple, closed-form analytical expressions can be used to quickly assess the radiation characteristics for a range of designs. These simple yet compelling guidelines should help to actualize the significant potential of metasurface antennas for dynamically reconfigurable apertures.

Manipulating the thermal-transport properties of solids is of great technological interest for heat management. This study investigates the influence of polarization and crystal structure on the room-temperature thermal conductivity $\kappa$ of epitaxial thin films of ferroelectric BiFeO${}_3$. $\kappa$ shows only slight dependence on ferroelectric domain-wall density, but depends significantly on crystal structure. This may provide a route to reversible control of thermal properties through the morphotropic phase transition between the two structures of BiFeO${}_3$.

Safeguarding spent nuclear fuel is challenging, with contrary requirements of on the one hand hermetically sealing repositories of highly radioactive material to avoid leakage or proliferation, while on the other hand allowing for monitoring. The authors use computer simulations to show that these difficulties can be ameliorated by probing the neutrino flux that is inevitably emitted by spent nuclear fuel, and which penetrates any shielding or overburden. With existing technology, never mind detector concepts currently in prototyping, this method has the potential to play an important role in a multifaceted approach to radioactive waste management.

The development of nanostructures and metamaterials with tunable and switchable properties attracts attention worldwide, for both the complex physics involved and the prospects for applications. One approach is to combine metamaterials with liquid crystals (LCs), but so far not much functionality has been gained beyond that of conventional LC devices. The authors analyze the physics and performance of a promising hybrid arrangement: an interdigitated subwavelength plasmonic grating covered with a nematic LC. This system’s fast, low-voltage switching is due to plasmon resonances driving LC modulation within just a tiny surface layer.