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Nanostructured surfaces enhance ion yields in matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). The spike protein complex, S1, is one fingerprint signature of Sars-CoV-2 with a mass of 75 kDa. Here, we show that MALDI-MS yields of Sars-CoV-2 spike protein ions in the 100 kDa range are enhanced 50-fold when the matrix-analyte solution is placed on substrates that are coated with a dense forest of multi-walled carbon nanotubes, compared to yields from uncoated substrates. Nanostructured substrates can support the development of mass spectrometry techniques for sensitive pathogen detection and environmental monitoring.

Heteroatom substitution can favorably alter electronic transport in conductive polymers to improve their thermoelectric performance. This study reports the spectroscopic, structural, and thermoelectric properties of poly(3-(3′,7′-dimethyloctyl) chalcogenophenes) or P3RX doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), where the heteroatom [X = thiophene (T), selenophene (Se), tellurophene (Te)], the doping methodology, and extent of doping are systematically varied. Spectroscopic measurements reveal that while all P3RX polymers are appreciably doped, the doping mechanism is inherently different. Poly(3-hexylthiophene) (P3HT, used as a control) and poly(3-(3′,7′-dimethyloctyl)tellurophene) (P3RTe) are doped primarily via integer charge transfer (ICT), whereas poly(3-(3′,7′-dimethyloctyl)selenophene) (P3RSe) and poly(3-(3′,7′-dimethyloctyl)thiophene) (P3RT) are doped via charge transfer complex (CTC) mechanisms. Despite these differences, all polymers saturate with roughly the same number of F4TCNQ counterions (1 dopant per 4 to 6 heterocycles), reinforcing the idea that the extent of charge transfer varies with the doping mechanism. Grazing incidence wide-angle x-ray scattering measurements provide insight into the structural driving forces behind different doping mechanisms—P3RT and P3RSe have similar microstructures in which F4TCNQ intercalates between the π-stacked backbones resulting in CTC doping (localized carriers), while P3HT and P3RTe have microstructures in which F4TCNQ intercalates in the alkyl side chain region, giving rise to ICT doping (delocalized carriers). These structural and spectroscopic observations shed light on why P3HT and P3RTe obtain electrical conductivities ca. 3 S/cm, while P3RT and P3RSe have conductivities

We have demonstrated a complementary metal-oxide-semiconductor inverter logic gate by heterogeneous integration of an enhancement-mode n-channel transistor on GaN and a p-channel transistor on diamond. A thermally grown p-type NiOx is used as the dielectric, and Ni/Au is the gate metal for both transistors. NiOx oxide on top of a partially recessed-gate AlGaN/GaN heterostructure depletes the two-dimensional electron gas by pulling the Fermi level closer to the valence band and making it normally OFF. The combination of Ni/NiOx gate metal work function and the dielectric helps to deplete the two-dimensional hole gas channel of a hydrogen-terminated p-channel diamond, making it an enhancement mode. The GaN n-MOS and diamond p-MOS transistors show output and transfer characteristics with threshold voltages of +0.6 and −1.2 V, respectively. nMOS and pMOS transistors show ION/IOFF current ratios of >105 and >103, respectively, with a subthreshold leakage of <10 μA/mm. The gate current is negligible for both devices. The saturation drain current of the respective transistors is measured to be ∼170 and ∼20 mA/mm at a gate-to-source overdrive voltage of 3 V. The inverter input–output characteristics and transient response are measured for various rail-to-rail voltages and frequencies. The inverter threshold voltage is measured to be 1.1 V for a nominal operating voltage of 3 V. [ABSTRACT FROM AUTHOR]

Light-emitting devices that take advantage of the wide bandgap characteristics of InGaN/GaN are widely used in the industry. However, inhomogeneities have been reported in their photoluminescence (PL) mapping at the nanometer and submicrometer scale, even in samples of high crystal quality. In addition, a blinking phenomenon (time variation of PL intensity) under photoexcitation has been reported in relation to these inhomogeneities. The reason why this blinking phenomenon occurs is still unclear; it has been observed in quantum dots and other single and multilayer quantum well structures. Nevertheless, there are very few publications on nanopillar InGaN quantum well samples, which are the focus of this research. Here, we report and analyze the behavior of the blinking phenomena on a nanopillar sample. We noticed that the blinking of the pillars is somehow synchronized on a long timescale among several spatially separated nanopillars. We demonstrated that the synchronization is not due to random intensity fluctuations. We suggest instead that the synchronization is caused by a nonlinear response of the quantum wells to the UV source. In other words, when the stimulation intensity surpasses a certain value, it triggers an ON/OFF state switch in the PL of some of the pillars. Even if preliminary, our study helps to provide clues to understanding the mechanism of the occurrence of the blink phenomenon. [ABSTRACT FROM AUTHOR]

High-resolution (sub-%), single-shot energy distribution, and emittance measurements of GeV-class electron beams generated by laser plasma accelerators (LPAs) have been enabled through the use of an active plasma lens combined with relatively short dipole magnets. This setup, with only 60 cm between the LPA source and the final diagnostic screen, was facilitated through the use of a replenishable ∼20-40 nm thick liquid crystal plasma mirror to separate remnant laser radiation from the electron beam without emittance degradation. As LPAs capable of generating GeV-class electron beams at cm-scale distances become increasingly ubiquitous, there is a need to supplement these compact accelerators with equally compact diagnostics.

Magnetic skyrmions are topologically protected spin textures with promising prospects for applications in data storage. They can form a lattice state due to competing magnetic interactions and are commonly found in a small region of the temperature - magnetic field phase diagram. Recent work has demonstrated that these magnetic quasi-particles fluctuate at the μeV energy scale. Here, we use a coherent x-ray correlation method at an x-ray free-electron laser to investigate these fluctuations in a magnetic phase coexistence region near a first-order transition boundary where fluctuations are not expected to play a major role. Surprisingly, we find that the relaxation of the intermediate scattering function at this transition differs significantly compared to that deep in the skyrmion lattice phase. The observation of a compressed exponential behavior suggests solid-like dynamics, often associated with jamming. We assign this behavior to disorder and the phase coexistence observed in a narrow field-window near the transition, which can cause fluctuations that lead to glassy behavior.

A non-standing characteristic of directly imaged spin-waves in confined micrometer-sized ultrathin Permalloy (Ni 80 Fe 20) structures is reported along with evidence of the possibility to alter the observed state by modifications to the sample geometry. Using micromagnetic simulations, the presence of the spin-wave modes excited in the Permalloy stripes along with the quasi-uniform modes was observed. The predicted spin-waves were imaged in direct space using time resolved scanning transmission X-ray microscopy, combined with a ferromagnetic resonance excitation scheme (STXM-FMR). STXM-FMR measurements revealed a non-standing characteristic of the spin-waves. Also, it was shown by micromagnetic simulations and confirmed using STXM-FMR results that the observed characteristic of the spin-waves can be influenced by the local magnetic fields in different sample geometries.

SnS has recently been shown to possess unique valleytronic capability with a large polarization degree, where non-degenerate valleys can be accessed using linearly polarized light, bestowed upon by the unique anisotropy and wavefunction symmetry. It is thus of utmost importance to demonstrate the extension of such effects for the IV-VI system in general, thereby elucidating the generality and tunability of such valleytronics. We show the highly tunable valleytronics via gradual compositional control of the tin(II) sulfo-selenide (SnSxSe1-x) alloy system with excellent retainment of symmetry-determined selection rules. We show the presence of both ΓY and ΓX valleys in all alloy compositions via selectivity in absorption and emission of linearly polarized light by optical reflection (R)/transmission (T) and photoluminescence measurements and tuned the bandgaps of the valleys within a range of 1.28 eV-1.05 eV and 1.48 eV-1.24 eV, respectively. This simultaneous tuning of non-degenerate valleys agrees well with theoretical calculations. We then fitted the bandgap values in compositional space, obtaining bowing parameters as a useful database. We further demonstrated the feasibility of using IV-VI valleytronics systems in general by elucidating the retainment of strong polarization degrees of as high as 91% across all compositions. The generalization of such purely symmetry-dependent valleytronics also opens up opportunities for the discovery of more multi-functional materials.

Spin-transfer torque magnetic tunneling junction devices capable of a multilevel three-dimensional (3D) information processing are studied in the sub-20-nm size range. The devices are built using He+ and Ne+ focused ion beam etching. It has been demonstrated that due to their extreme scalability and energy efficiency, these devices can significantly reduce the device footprint compared to the modern CMOS approaches and add advanced features in a 3D stack with a sub-20-nm size using a spin polarized current.

Low-temperature X-ray photoemission electron microscopy (X-PEEM) is used to measure the electric potential at domain walls in improper ferroelectric Er0.99Ca0.01MnO3. By combining X-PEEM with scanning probe microscopy and theory, we develop a model that relates the detected X-PEEM contrast to the emergence of uncompensated bound charges, explaining the image formation based on intrinsic electronic domain-wall properties. In contrast to previously applied low-temperature electrostatic force microscopy (EFM), X-PEEM readily distinguishes between positive and negative bound charges at domain walls. Our study introduces an X-PEEM-based approach for low-temperature electrostatic potential mapping, facilitating nanoscale spatial resolution and data acquisition times on the order of 0.1-1 s.

In this study, we report on a shape-imposed magnetic anisotropy in micro- and nanostructures defined in antiferromagnetic (AF) LaFeO3 (LFO) thin films. Two distinct types of structures are investigated: embedded magnets created via ion implantation and free-standing magnets created via ion milling. Using a combination of x-ray photoemission electron microscopy and x-ray absorption spectroscopy, we examine the impact of the structure type, AF layer thickness, and crystal geometry on the Néel vector orientation in these structures. We demonstrate a distinct shape-imposed anisotropy in embedded and free-standing structures alike and show that both parallel and perpendicular alignments of the AF spin axis with respect to structure edges can be achieved by variation of the AF layer thickness and the orientation of the structure edges with respect to the LFO crystalline axes. This work demonstrates how the fabrication procedure affects the magnetic order in thin film AF nanostructures and shows how nanoscale patterning can be used to control the orientation of the Néel vector in epitaxial oxide thin films.

In this letter, we demonstrate that improved low energy electron absorption is achieved by suppressing the crystallinity of chromium thin-films grown on W[110], which points to a promising route for achieving highly efficient thermionic energy converters. Using low energy electron microscopy (LEEM) and in situ film growth, we show that substrate temperature control permits well-controlled fabrication of either epitaxial Cr[110] films or nanocrystalline Cr layers. We show that the work function of cesium saturated nanocrystalline Cr thin-films is ∼0.20 eV lower than that of epitaxial Cr[110] films. Our LEEM measurements of absorbed and reflected currents as a function of electron energy demonstrate that nanocrystallinity of cesiated chromium films results in 96% electron absorption in the range up to 1 eV above the work function, compared to just 79% absorption in cesiated crystalline Cr[110] films. These results point to metal films with suppressed crystallinity as an economical and scalable means to synthesize nanoengineered surfaces with optimized properties for next generation anode materials in high performance thermionic energy converters.

Transition metal dichalcogenide (TMDC) monolayers are promising materials for next-generation nanoscale optoelectronics, including high-speed light sources and detectors. However, most past reports on TMDC light-emitting diodes are limited to operation in high vacuum, while most applications require operation under ambient conditions. In this work, we study the time-resolved electroluminescence of monolayer WSe2 p-n junctions under ambient conditions and identify the decay in current over time as the main issue preventing stable device operation. We show that pulsed voltage bias overcomes this issue and results in bright electroluminescence under ambient conditions. This is achieved in a simple single-gate structure, without the use of dual gates, heterostructures, or doping methods. Internal quantum efficiency of electroluminescence reaches ∼1%, close to the photoluminescence quantum efficiency, indicating efficient exciton formation with injected carriers. Emission intensity is stable over hours of device operation. Finally, our device exhibits ∼15 ns rise and fall times, the fastest direct modulation speed reported for TMDC light-emitting diodes.

We study the effect of carbon segregants on the spin and orbital moments of L10 FePt granular media using x-ray magnetic circular dichroism (XMCD) spectroscopy and report an effective decoupling of the structural film properties from the magnetic parameters of the grains. The carbon concentration reduces the grain size from (200 ± 160) nm2 down to (50 ± 20) nm2 for 40 mol. %C and improves sphericity and the order of grains, while preserving the crystalline order, spin and orbital moments, and perpendicular magnetocrystalline anisotropy. We identify the primary cause of enhanced saturation and coercive fields as the reduced demagnetization fields of individual grains. The ability to shrink grains without impairing their magnetic properties is a critical requirement for the commercialization of Heat-Assisted Magnetic Recording.

Kagome metal ScV6Sn6 has been a subject of interest due to the emergence of a first-order structural phase transition with intriguing charge density wave behavior below the transition temperature Tc ∼ 92 K. To explore the thermoelectric properties and provide experimental insights into the nature of the phase transition, we have carried out a combined study by means of the electrical resistivity, Seebeck coefficient, and thermal conductivity measurements on single crystalline ScV6Sn6. Pronounced features near Tc have been characterized by all measured physical quantities. In particular, the Seebeck coefficient exhibits a marked reduction as lowering temperature across Tc, attributed to an imbalance of the contribution from different type of carriers induced by the structural phase transition. From the examination of the electronic and lattice thermal conductivities, we obtained a confirmation that the observed enhancement at Tc is essentially caused by the change of the lattice thermal conductivity, demonstrating the primary importance of lattice distortions for the heat transport of ScV6Sn6. In addition, the lattice thermal conductivity above Tc was found to increase monotonically with temperature. We associated the peculiar phenomenon with lattice fluctuations, highlighting the essence of structural instability in the kagome lattice ScV6Sn6. These results add to the knowledge about the thermal transport properties in kagome materials with a hexagonal HfFe6Ge6-type structure. [ABSTRACT FROM AUTHOR]

Rydberg atom electric field sensors are tunable quantum sensors that can perform sensitive radio frequency measurements. Their qualities have piqued interest at longer wavelengths where their small size compares favorably to impedance-matched antennas. Here, we compare the signal detection sensitivity of cm-scale Rydberg sensors to similarly sized room-temperature electrically small antennas with active and passive receiver backends. We present and analyze effective circuit models for each sensor type, facilitating a fair sensitivity comparison for cm-scale sensors. We calculate that contemporary Rydberg sensor implementations are less sensitive than unmatched antennas with active amplification. However, we find that idealized Rydberg sensors operating with a maximized atom number and at the standard quantum limit may perform well beyond the capabilities of antenna-based sensors at room temperature, the sensitivities of both lying below typical atmospheric background noise. [ABSTRACT FROM AUTHOR]

This study investigates the destructive breakdown (DBD) phenomenon in the van der Waals gate dielectric 2D muscovite mica (4–12 nm thick), focusing on its electrical reliability as a gate dielectric material. Capacitor test structures were electrically stressed, and the resulting impact on the physical structure was analyzed using atomic force microscopy. The volume of material removed in a DBD event is found, and the energy required (Ereq) to vaporize the volume was calculated. It is found that Ereq is proportional to the average electrical energy dissipated in the capacitor during breakdown (BD), indicating a direct correlation between damage caused during DBD and the current flow at BD location. In contrast to other thin film dielectrics, the 2D mica is highly susceptible to DBD even at very low current density (<1 A/cm2) and the abrupt, destructive BD more resembles that of thick film dielectric breakdown. An explanation for these finding is proposed in which intercalated K+ ions agglomerate around defects generated by the electrical stressing such that the defect density increases substantially in the local vicinity of BD locations, which leads to increased current and associated Joule heating after the BD event. [ABSTRACT FROM AUTHOR]

A field-driven transformation of a domain pattern in a square micromagnet, defined in a thin film of La0.7Sr0.3MnO3, is discussed in terms of creation and annihilation of bulk vortices and edge-bound topological defects with half-integer winding numbers. The evolution of the domain pattern was mapped with soft x-ray photoemission electron microscopy and magnetic force microscopy. Micromagnetic modeling, permitting detailed analysis of the spin texture, accurately reproduces the measured domain state transformation. The simulations also helped stipulate the energy barriers associated with the creation and annihilation of the topological charges and thus to assess the stability of the domain states in this magnetic microstructure.

In this work, brain-like experiential learning/forgetting ability is demonstrated with the help of various synaptic adaptation rules, namely, short-term potentiation/short-term depression, long-term potentiation/long-term depression, spike rate-dependent plasticity, and spike-time-dependent plasticity in a thin-film device. The model device used here is a unidirectional thin film of nanocrystalline Co3O4, grown on a p-Si (100) substrate using the pulsed laser deposition technique to fabricate a metal–insulator–semiconductor type memristor. Along with this, we found an analog bipolar-type switching behavior with excellent resistive switching properties in terms of endurance, retention, and ON–OFF ratio suitable for CMOS-based memory applications. The conduction and resistive switching mechanisms are elucidated using a speculative band diagram formulated from the UV-visible spectroscopy data. [ABSTRACT FROM AUTHOR]

Surface-gated quantum dots (QDs) in semiconductor heterostructures represent a highly attractive platform for quantum computation and simulation. However, in this implementation, the barriers through which the QD is tunnel-coupled to source and drain reservoirs (or neighboring QDs) are usually non-rigid and capacitively influenced by the plunger-gate voltage ( V P ). In transport spectroscopy measurements, this leads to suppression of current and lifting of the Coulomb blockade for increasing negative and positive values of V P , respectively. Consequently, the charge-occupancy of the QD can be tuned over a rather small range of V P . By dynamically tuning the tunnel barriers to compensate for the capacitive effect of V P , here we demonstrate a protocol that allows Coulomb blockade to be preserved over a remarkably large span of charge-occupancies, as demonstrated by clean Coulomb diamonds and well-resolved excited state features. The protocol will be highly beneficial for automated tuning and identification of the gate voltage space for optimal operation of QDs in large arrays required for a scalable spin quantum computing architecture. [ABSTRACT FROM AUTHOR]

Applying voltage to metal–insulator transition (MIT) materials allows electrical actuation of the local electronic phase state. In MIT systems that have the electronic order coupled with the magnetic order, voltage switching of the electronic phase state can also enable the electrical manipulation of magnetic properties. In this work, we utilized x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) to investigate the control of magnetic domain configurations in ferromagnetic MIT electrical switches. For applied voltages above a threshold value, the XMCD-PEEM images show that the magnetic domains separate into two distinct regions: one with a high contrast (white/black), indicating well-defined micrometer-scale magnetic domains with a component of their magnetization aligned parallel/antiparallel to the x-ray helicity, and the other with different shades of intermediate contrast (gray). Significant changes in magnetic domain configurations upon voltage biasing were only observed in these gray regions. Furthermore, the voltage-induced magnetic domain separation was found to be bias polarity-dependent, with the gray regions expanding from the opposite sample edge when the applied voltage polarity was reversed. This polarity-dependent electrical control of magnetic domain configurations during the MIT switching opens alternative opportunities in memory applications for magnetic MIT switching materials. [ABSTRACT FROM AUTHOR]

The intrinsic antisite defects, which cause doping in the antiferromagnetic topological insulators of the MnTe · n Bi2Te3 (n = 1, 2, 3, ...,) family, prevent the exploration of the Dirac states affecting the Fermi level ( E F ) position and magnetic properties. In the present study, the MnTe · Bi(2−x)Te3(1−x/2) films grown by the MBE technique onto Si(111) substrates with increasing the Bi and Te contents from MnTe to MnBi2Te4 were investigated by 0.5–6.5 eV spectroscopic ellipsometry. In addition, the infrared (IR) reflectance and transmittance spectra were examined. The measured ellipsometric angles, Ψ (ω) and Δ (ω) , were simulated in a two- or three-layer Gaussian models. As a result, the spectra of the complex dielectric function, ε ̃ (ω) = ε 1 (ω) + i ε 2 (ω) , the complex index of refraction, n ̃ (ω) = n (ω) + i k (ω) , and the optical conductivity σ 1 (ω) were determined. We found that the absolute values of the ε 1 (ω) and ε 2 (ω) increased with increasing the Bi and Te contents from MnTe to MnBi2Te4, while the ε 2 (ω) maximum progressively shifts to lower photon energies from ∼ 3.7 to ∼ 1.2 eV, peculiar of the end point compounds. At the same time, the stoichiometric MnBi2Te4 film exhibits the emergent Drude-type contribution in the far-IR range associated with the intrinsic antisite doping. However, the charge carrier contribution is suppressed in the MnTe · Bi(2−x)Te3(1−x/2) films with the reduced Bi and Te stoichiometry, the latter being also responsible for the electronic band structure reconstruction and pronounced redistribution of the optical spectral weight. [ABSTRACT FROM AUTHOR]

Nonlinear optical materials are essential for the development of both nonlinear and quantum optics and have advanced recently from bulk crystals to integrated material platforms. In this Perspective, we provide an overview of the emerging InGaP χ (2) nonlinear integrated photonics platform and its experimental achievements. With its exceptional χ (2) nonlinearity and low optical losses, the epitaxial InGaP platform significantly enhances a wide range of second-order nonlinear optical effects, from second-harmonic generation to entangled photon pair sources, achieving efficiencies several orders of magnitude beyond the current state of the art. Moreover, the InGaP platform enables quantum nonlinear optics at the few- and single-photon levels via passive nonlinearities, which has broad implications for quantum information processing and quantum networking. We also examine the current limitations of the InGaP platform and propose potential solutions to fully unlock its capabilities. [ABSTRACT FROM AUTHOR]

Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling. [ABSTRACT FROM AUTHOR]

The study of phonon coupling in doped semiconductors via electrical transport measurements is challenging due to unwanted temperature-induced effects such as dopant ionization and parallel conduction. Here, we study phonon scattering in 2D electrons and holes in the 1.6 – 92.5 K range without the use of extrinsic doping, where both acoustic and longitudinal optic (LO) phonons come into effect. We use undoped GaAs/ Al x Ga 1 − x As heterostructures and examine the temperature dependence of the sample resistivity, extracting phonon coupling constants and the LO activation energy. Our results are consistent with results obtained through approaches other than transport measurements and highlight the benefit of this approach for studying electron–phonon and hole–phonon coupling. [ABSTRACT FROM AUTHOR]

The generation of single photons using solid-state quantum emitters is pivotal for advancing photonic quantum technologies, particularly in quantum communication. As the field continuously advances toward practical use cases and beyond shielded laboratory environments, specific demands are placed on the robustness of quantum light sources during operation. In this context, the robustness of the quantum light generation process against intrinsic and extrinsic effects is a major challenge. Here, we present a robust scheme for the coherent generation of indistinguishable single-photon states with very low photon number coherence using a three-level system in a semiconductor quantum dot. Our approach combines the advantages of adiabatic rapid passage and stimulated two-photon excitation. We demonstrate robust quantum light generation while maintaining the prime quantum-optical quality of the emitted light state. Moreover, we highlight the immediate advantages of the implementation of various quantum cryptographic protocols. [ABSTRACT FROM AUTHOR]

Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling. [ABSTRACT FROM AUTHOR]

In fiber spinning of photopolymers, surface tension limits the diameter of the fiber that can be produced due to the Rayleigh–Plateau instability. Submerging a pre-fiber jet in a miscible environment liberates the system from capillary effects, thus allowing the jet to be stretched into thin threads without instability. In this work, we systematically investigated a spinning method using miscible liquids, called jet-assisted wet spinning (JAWS), where stretching is achieved by a nearby submerged liquid jet. The diameter of the pre-fiber jet is a function of its flow rate and position relative to the assisting submerged liquid jet. A particular case where the main jet is modeled as the Landau–Squire jet is used to demonstrate the tracer-like thinning behavior of the pre-fiber jet. Experiments show that buoyancy has a significant impact on the pre-fiber jet diameter because of its influence on the entrainment trajectory. Overall, our results demonstrate the potential for the parallelization of JAWS for high-throughput fiber production. [ABSTRACT FROM AUTHOR]

van der Waals topological insulators, characterized by their high-index dielectric response, offer a promising materials platform for nanophotonics. Among these materials, Bi2Te3 has one of the highest refractive indices and extinction coefficients. However, the precise determination of Bi2Te3 optical properties remains challenging owing to its complicated physical model, which includes an oxide layer, topological conducting states, and optical anisotropy. Here, we resolve this problem and develop an accurate optical model for Bi2Te3 in a broad (450–1500 nm) spectral range. Our study shows that an oxide layer plays a major role in optical model for these wavelengths, while the influence of topological conducting states and optical anisotropy is minimal. Our model allows us to obtain accurate Bi2Te3 optical constants and demonstrate their use in biosensors, thermal theranostics, and topological phase singularities. Moreover, we observe a polarization transition of topological phase singularity for Bi2Se3, which opens a new direction for the development of topological phase effects. Therefore, our results open new avenues for photonic applications of Bi2Te3 optical properties. [ABSTRACT FROM AUTHOR]

Using a successive detection technique with electron spin resonance (ESR) and electrically detected magnetic resonance (EDMR), this study clarifies the quantitative correlation between photoinduced spin amounts and spin-dependent recombination (SDR) currents in organic photovoltaic devices (OPVs). Using this unique method of sequentially switching between ESR and EDMR measurements under light irradiation, we find that the intensities of light-induced ESR and EDMR spectra increase along with the light irradiation power. Although positive correlation exists between the number of photo-generated radicals and the SDR currents, the relation is not proportional, which demonstrates that most of the photo-generated radicals are residual accumulated charges. Additionally, phases of the EDMR spectra under light irradiation were found to be changed because of a delay of modulated EDMR signals. The phase variation is probably caused by recombination centers: positive polarons that have arrived at the interface between an aluminum electrode and an active layer by charge drifting after charge separation. Because positive polarons are expected to transport positive charges to the opposite-side electrode of the aluminum as a negative charge collector, this leakage current can be a factor of disturbing an optimal charge collection. This combined technique of ESR and EDMR is useful to explore the different roles of polarons in the photovoltaic conversion processes, thereby providing important information for improving the fill factors and open-circuit voltages of the OPVs, which generate long-lived polarons. [ABSTRACT FROM AUTHOR]

Experimental searches for axions or dark photons that couple to the standard model photon require photosensors with low noise, broadband sensitivity, and near zero backgrounds. Here, we introduce an experimental architecture, in which a small photon sensor, in our case a transition edge sensor (TES) with a photon energy resolution σ γ = 368.4 ± 0.4 meV, is colocated on the same substrate as a large high sensitivity athermal phonon sensor (APS) with a phonon energy resolution σ phonon = 701 ± 2 meV. We show that single 3.061 eV photons absorbed in the photon-sensing TES deposit ∼ 35% of their energy in the electronic system of the TES, while ∼ 26% of the photon energy leaks out of the photon-sensing TES during the downconversion process and becomes absorbed by the APS. Backgrounds, which we associate with the broadly observed "low energy excess" (LEE), are observed to be largely coupled to either the TES ("singles" LEE), or phonon system, ("shared" LEE). At high energies, these backgrounds can be efficiently discriminated from TES photon absorption events, while at low energies, their misidentification as photon events is well modeled. With significant sensitivity improvements to both the TES and APS, this coincidence technique could be used to suppress backgrounds in bosonic dark matter searches down to energies near the superconducting bandgap of the sensor. [ABSTRACT FROM AUTHOR]

Room-temperature photoluminescence (PL) spectra of intensely pumped HgTe/CdHgTe quantum well (QW) heterostructures emitting at around 5 μm wavelength have been investigated. Based on the model description of the PL spectra using a free-electron recombination band approach, effective electronic temperatures were determined depending on the excitation density. Within the quasi-steady-state approximation, we establish the balance between pump-induced heating of the electron gas in the QWs and phonon-mediated dissipation of this excess energy and deduce hot-phonon lifetime of ∼0.47 ps. Maximum operating temperatures for optically pumped HgTe/CdHgTe QW laser heterostructures emitting at around 5 μm are estimated depending on the excitation wavelength, and lasing at Peltier temperatures appears feasible for the pump wavelength of about 3 μm. Thus, the entire 3∼5 μm atmospheric transparency window can be potentially covered by thermoelectrically cooled HgCdTe-based laser sources. [ABSTRACT FROM AUTHOR]

In this work, we study the acoustic forces acting on particles due to sound scattering at the interface with an elastic substrate. Utilizing the Green's function formalism, we predict that excitation of a leaking Rayleigh wave results in a strong modification of the acoustic pressure force acting on a monopole scatterer and changes the equilibrium position of particles above the substrate surface. We also showed that the presence of a substrate changes the configuration of the acoustical binding of two particles due to multiple rescattering of acoustic waves from the interface. The reported results propose the method of acoustic manipulation via surface wave excitation and demonstrate the effect of elastic media in acoustical trapping of micro-objects. [ABSTRACT FROM AUTHOR]

Atmospheric pressure nonequilibrium plasma holds significant potential in biomedical applications due to its ability to generate reactive species at low temperatures. However, accurately quantifying and controlling plasma dosage remains challenging. Although equivalent total oxidation potential (ETOP) has been proposed for defining dosage, previous methods required measurement of various reactive oxygen and nitrogen species (RONS) densities, which are impractical in diverse plasma settings. Efficient ETOP prediction across variable conditions is thus essential. To address this, we propose a machine learning-based ETOP modeling method. This study collected RONS density data under various conditions using laser-induced fluorescence and trained an artificial neural network to predict ETOP values based on input parameters like voltage, gas flow rate, oxygen concentration, and humidity. This approach enables efficient ETOP prediction across variable conditions, supporting the standardization and clinical application of plasma medicine. [ABSTRACT FROM AUTHOR]

In a nanomechanical resonator coupled to a quantum point contact, the back action of the electronic state on mechanical motion is studied. The quantum point contact conductance changing with subband index and the eigenfrequency of the resonator are found to correlate. A model is constructed explaining the frequency deviations by the variable ability of the quantum point contact to screen the piezoelectric charge induced by mechanical oscillations. The observed effects can be used to develop electromechanical methods for studying the density of states in quasi-one-dimensional systems. [ABSTRACT FROM AUTHOR]

We present results from time-resolved X-ray imaging and inelastic scattering on collective excitations. These data are then employed to infer the mass density evolution within laser-driven shock waves. In our experiments, thin carbon foils are first strongly compressed and then driven into a dense state by counter-propagating shock waves. The different measurements agree that the graphite sample is about twofold compressed when the shock waves collide, and a sharp increase in forward scattering indicates disassembly of the sample 1 ns thereafter. We can benchmark hydrodynamics simulations of colliding shock waves by the X-ray scattering methods employed.