Browse Articles

Hanle spin precession induced inverted magnetoresistance in chiral/semiconductor systems

In the past decade, chiral materials have drawn significant attention because it is widely claimed that they can act as spin injectors/detectors due to the chirality-induced spin selectivity effect. Nevertheless, the microscopic origin of this effect is not understood, which generates the need for transport experiments that confirm the spin-dependent transport in chiral materials. Hanle spin precession measurements can unambiguously prove the injection and detection of a spin accumulation in a non-magnetic material, as was shown with traditional ferromagnetic injectors/detectors. Here, we model and analyze in detail the Hanle spin precession-induced magnetoresistance for chiral/semiconductor systems and find that the signal is inverted as compared to the ferromagnetic case. We explicitly model the spin injection and detection by both a chiral system and a ferromagnetic system, as well as the spin transport in a semiconductor, for a general set of (spin) transport parameters that cover the relevant experimental regime. For all sets of parameters, we find that the Hanle signals for a chiral system and ferromagnet are each other's opposites. We also discuss the implications for four terminal nonlocal spin transport experiments with separate chiral spin injector and detectors.

Fluorescein-based SynNotch adaptors for regulating gene expression responses to diverse extracellular and matrix-based cues

Te nanomesh-monolayer WSe2 vertical van der Waals heterostructure for high-performance photodetector

Recently, two-dimensional tungsten diselenide (WSe2) has attracted extensive attention due to their unique properties, exhibiting excellent properties in electronics, optoelectronics, and valleytronics. However, the limited light absorption efficiency of monolayer WSe2 severely hinders its practical applications. To address this challenge, vertical Te-WSe2 heterojunctions consisting of Te nanomesh and monolayer WSe2 nanofilm have been prepared using the two-step vapor deposition method, which significantly enhances the optoelectronic performance. Te-WSe2 heterojunction photodetector exhibits a high responsivity of 1.3 A/W and a specific detectivity of 1 × 1010 Jones under the irradiation of 460 nm light source. This study demonstrates the controllable fabrication of large-scale of Te-WSe2 vertical heterojunctions. The underlying mechanism for the performance enhancement of Te-WSe2 heterojunction photodetector was elucidated based on the Ohm-like type-I band-aligned structure. The research can be further extended to other Te-based mixed-dimensional heterojunctions, providing valuable theoretical and experimental support for the application of next-generation integrated optoelectronic devices.

Camel milk is a neglected source of brucellosis among rural Arab communities

Abstract The World Health Organization describes brucellosis as one of the world’s leading zoonotic diseases, with the Middle East a global hotspot. Brucella melitensis is endemic among livestock populations in the region, with zoonotic transmission occurring via consumption of raw milk, amongst other routes. Control is largely via vaccination of small ruminant and cattle populations. Due to sociocultural and religious influences camel milk (camelus dromedarius) is widely consumed raw, while milk from other livestock species is largely boiled. To investigate the potential public health impact of Brucella in camels we conduct a cross-sectional study in southern Jordan including 227 herds and 202 livestock-owning households. Here we show daily consumption of raw camel milk is associated with Brucella seropositive status among the study population, ORadj 2.19 (95%CI 1.23–3.94) on multivariable analysis, highlighting the need for socioculturally appropriate control measures; targeted interventions among the camel reservoir being crucial for effective control.

Fabrication and characterization of heteroepitaxial Zn2GeO4 films on sapphire via radio frequency magnetron sputtering

In this study, we explored the fabrication, structural characteristics, and optical properties of Zn2GeO4 thin films grown on c-cut Al2O3 substrates via radio frequency magnetron sputtering. The crystalline quality, surface morphology, and optical characteristics were comprehensively evaluated at various annealing temperatures, and the 700 °C-annealed film presented the best crystallization quality. XRD and TEM results revealed the microstructure of Zn2GeO4 film and confirmed that the epitaxial relationship is Zn2GeO4 (0006)//Al2O3 (0006) with Zn2GeO4 [11¯00]//Al2O3 [11¯00]. O 1s spectrum indicated the bandgap of the 700 °C-annealed film is 4.98 eV. UV-Vis-Near Infrared spectroscopy showed that the average transmittance reached approximately 85% in the visible region, and the optical bandgap of Zn2GeO4 film annealed at 700 °C was about 5.02 eV.

Non-linear enhancement of ultrafast X-ray diffraction through transient resonances

Abstract Diffraction-before-destruction imaging with ultrashort X-ray pulses can visualize non-equilibrium processes, such as chemical reactions, with sub-femtosecond precision in the native environment. Here, a nanospecimen diffracts a single X-ray flash before it disintegrates. The sample structure can be reconstructed from the coherent diffraction image (CDI). State-of-the-art X-ray snapshots lack high spatial resolution because of weak diffraction signal. Bleaching effects from photo-ionization significantly restrain image brightness scaling. We find that non-linear transient ion resonances can overcome this barrier if X-ray laser pulses are shorter than in most experiments. We compared snapshots from individual  ≈ 100 nm Xe nanoparticles as a function of pulse duration and incoming X-ray fluence. Our experimental results and Monte Carlo simulations suggest that transient resonances can increase ionic scattering cross sections significantly beyond literature values. This provides a novel avenue towards substantial improvement of the spatial resolution in CDI in combination with sub-femtosecond temporal precision at the nanoscale.

Physics-informed genetic algorithms (PIGAs) facilitating LIBS spectral normalization with shockwave characteristics

Inspired by physics-informed neural networks (PINNs) inheriting both the interpretability of physical laws and the efficient integration capability of machine learning, we propose a framework based on stoichiometric ablation for LIBS spectral normalization, encoding physical constraints between LIBS intensities and shockwave characteristics (temperature Tshock and pressure P) into optimization algorithms with multiple independent objectives, named physics-informed genetic algorithms (PIGAs). It is characterized by its applicability to the wider laser energy range, covering laser-induced breakdown to significant plasma shielding and spectral lines undergoing self-absorption, outperforming the widely used physical linear or multivariate data-driven normalization methods. The home-made end-to-end LAP-RTE codes serve as the benchmark to validate the physical reciprocal-logarithmic transformation and its extensibility to self-absorption spectral lines for PIGAs. Next, experimental spectral lines are statistically used to validate PIGAs' correction effects; the median RSDs of spectral intensities can be effectively reduced by 85% (corrected by P) and 88% (corrected by Tshock) for 108 Fe I lines, while for 33 Fe II lines, reduced by 77% (corrected by P) and 86% (corrected by Tshock). Seventeen self-absorption lines are also corrected effectively, with RSDs being reduced by 78% (corrected by P) and 89% (corrected by Tshock). Our proposed idea of combining optimization methods to quantify unknown parameters in normalization strategies can also be extended to excavate the correlation between parameters for other low-temperature plasma fields with similar processes.

Spatiotemporal transcriptome and metabolome landscapes of cotton fiber during initiation and early development

High-throughput screening and research of nitrogen reduction on 2D metal–organic framework: First-principles study

Developing efficient nitrogen reduction reaction (NRR) catalysts remains challenging. Two-dimensional metal–organic frameworks (MOFs) stand out because of their large holes and high metal utilization. Based on first-principles high-throughput calculations, we studied the catalytic capacity of MOF catalyst TM3 (HITP)2 for NRR. Our calculated results indicate that among 29 catalytic structures, Mo3(HITP)2 and Os3(HITP)2 exhibit excellent activity for NRR, with the overpotential being 0.39 and 0.43 V, respectively. The unoccupied 4d orbitals of Mo are especially closer to the antibonding N-2p orbitals, leading to better nitrogen activation and lower overpotential. In addition, a descriptor related to charge variation and the electronegativity of metals and coordinating atoms is established, which has a good volcano plot relationship with the limiting potential of NRR and can provide ideas for catalyst screening. This research contributes valuable insights for the screening of NRR catalysts based on MOF.

Super elastic and negative triboelectric polymer matrix for high performance mechanoluminescent platforms

Point defect diffusion in III-nitrides: A key mechanism for thermal degradation and non-radiative recombination in GaInN/GaN quantum well structures

Various forms of thermal degradation of light emitters based on III-nitrides have been observed, with no clear conclusion about the mechanism. We investigate the non-radiative carrier lifetime in GaInN/GaN single quantum wells (SQWs) with various emission wavelengths and its relation to the growth conditions. We observe that the non-radiative lifetime in SQWs increases exponentially with decreasing buffer and cladding layer growth temperature. As a first conclusion, diffusion of point defects leading to non-radiative recombination is a universal mechanism present during III-nitride growth. Second, this is likely a predominant mechanism for thermal degradation observed while growing layers on top of the quantum well, e.g., a p-layer, and after post-growth annealing. Performance and reliability of devices can be improved by properly controlling point defect diffusion.

Sun-simulated-driven production of high-purity methanol from carbon dioxide

Efficient spintronic THz emitters without external magnetic field

We investigate the performance of state-of-the-art spintronic THz emitters (W or Ta)/CoFeB/Pt with non-magnetic underlayer deposited using oblique angle deposition. The THz emission amplitude in the presence or absence of an external magnetic field remains the same and remarkably stable over time. This stability is attributed to the enhanced uniaxial magnetic anisotropy in the ferromagnetic layer, achieved by the oblique angle deposition of the underlying non-magnetic layer. Our findings could be used for the development of practical field-free emitters of linearly polarized THz radiation, potentially enabling applications in future THz technologies.

Reconstructing skeletal homeostasis through allogeneic hematopoietic stem cell transplantation in myelofibrosis

Abstract Myeloproliferative neoplasm-associated myelofibrosis is a clonal stem cell process characterized by pronounced bone marrow fibrosis associated with extramedullary hematopoiesis and splenomegaly. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) represents the only curative treatment leading to bone marrow fibrosis regression. Here we provide an in-depth skeletal characterization of myelofibrosis patients before and after allo-HSCT utilizing clinical high-resolution imaging, laboratory analyses, and bone biopsy studies. Despite unimpaired bone microarchitecture at peripheral skeletal sites, we observe a marked increase in bone mineral density at the lumbar spine and proximal femur, which is histologically related to severe bone marrow fibrosis and osteosclerosis, fully normalizing after allo-HSCT. Importantly, the regression of fibrosis is accompanied by vanishing osteosclerosis along with restored osteoclastic resorption activity and whole-body calcium homeostasis. Together, our results provide evidence for an extensive reconstruction of skeletal homeostasis by allo-HSCT in MF, leading to rapid resolution of osteosclerosis.

Investigating spin-orbit interaction of light in micro- and nanophotonic systems using polarization Mueller matrix

Coupling between the spin and orbital angular momentum of light has led to a variety of exotic spin–orbit photonic effects, establishing a paradigm of nanophotonic meta-devices to control and manipulate light at the nanometer length scale. For the advancement of spin–orbit photonic technologies, quantitative characterization and unambiguous physical interpretation of the various spin–orbit interaction (SOI) effects exhibited in complex nanophotonic systems are of utmost importance. This Perspective addresses some of these outstanding challenges in the domain of spin–orbit photonics, focusing on the simultaneous manifestation of multiple SOI effects in hybridized nanophotonic systems and the role of polarization-based techniques in their characterization and quantification. After introducing the fundamentals and physical origins of SOI effects, we present a polarization Mueller matrix technique as a powerful tool to probe, decouple, and independently quantify these effects in a unified experimental framework, demonstrated with hybridized waveguided plasmonic crystals. We further discuss the potential of structured light and tailored polarization to enable unconventional SOI phenomena in simple nanostructured metamaterials and metasurfaces. These advancements not only enhance our fundamental understanding of SOI phenomena across micro- and nanoscale optical systems but also pave the way for the development of multifunctional and tunable spin–orbit photonic devices.

Thermalization of a flexible microwave stripline measured by a superconducting qubit

With the demand for scalable cryogenic microwave circuitry continuously rising, recently developed flexible microwave striplines offer the tantalizing perspective of increasing the cabling density by an order of magnitude without thermally overloading the cryostat. We use a superconducting quantum circuit to test the thermalization of input flex cables with integrated 60 dB of attenuation distributed at various temperature stages. From the measured decoherence rate of a superconducting fluxonium qubit, we estimate a residual population of the readout resonator of (2.2±0.9)×10−3 photons and we measure a 0.28 ms thermalization time for the flexible stripline attenuators. Furthermore, we confirm that the qubit reaches an effective temperature of 26.4 mK, close to the base temperature of the cryostat, practically the same as when using a conventional semi-rigid coaxial cable setup.

Chiral correlated-plasmons enhanced Raman optical activity from spin-polarized, correlated <i>s</i> band in highly oriented single-crystalline gold quantum-dots

Interactions of chiral light with chiral matter, such as Raman optical activity (ROA) and, independently, spin-polarized materials have attracted a lot of interest for both fundamental science and applications. The ROA, on the one hand, provides information on chiral phonons of molecules. However, the short-lifetime ROA signal in general is extremely weak and requires long exposure times, making it not accessible for many important systems with short lifetime. Materials exhibiting high spin polarization in d or f band, on the other hand, remain very limited even at very low temperature. There has been no report on materials exhibiting spin polarization in s band. Herewith, we report a room temperature, full spin polarization in unconventional, correlated s band of highly oriented single-crystalline gold quantum-dots (HOSG-QDs). Intriguingly, the HOSG-QDs produce a chiral correlated-plasmons enhanced Raman optical activity (CP-ROA) with anomalous ROA enhancement and strong spin-dependent chiral coupling. We then address a fundamental problem in crystal violet. Using spin-polarized HOSG-QDs chips, we observe strong CP-ROA signal, revealing chiral properties. The chiral correlated-plasmons of HOSG-QDs interact with the spin, electronic, and lattice structures of crystal violet, revealing chiral phonons and chiral electronic Raman excitations of crystal violet. Such a strong CP-ROA spectrum is obtained within a minute of measurement and a simple preparation without patterning. Our result shows that the CP-ROA based on a spin-polarized HOSG-QDs is extremely sensitive to the chiral property of phonon and spin and electronic structures and a fast, label-free chiral spectroscopic-based detection.

Ultrahigh field-effect mobility of 147.5 cm2/Vs in ultrathin In2O3 transistors via passivating the surface of polycrystalline HfO2 gate dielectrics

This study presents considerable improvements in the electrical characteristics of atomic-layer-deposited 3-nm-thick In2O3 thin-film transistors (TFTs), which were achieved by introducing a 2-nm-thick amorphous Al2O3 interfacial layer to passivate the surface of a polycrystalline HfO2 gate dielectric. The resulting devices exhibited exceptional electrical characteristics, including an ultrahigh field-effect mobility (μFE) of approximately 147.5 ± 16.6 cm2/V s, subthreshold swing of 103.7 ± 9.1 mV/dec, and threshold voltage (VTH) of 0.5 ± 0.1 V. These enhancement-mode devices represent increases of more than threefold in μFE compared to devices without an amorphous passivation layer. This is despite all the fabrication processes being identical, except for the introduction of the Al2O3 interfacial layer. This improvement can be primarily attributed to the reduced electron scattering through suppressed remote Coulomb interactions. Furthermore, the In2O3 TFTs exhibited enhanced operational stability, showing minimal VTH shifts of 0.15 and −0.01 V under positive and negative bias-stress conditions, respectively. The findings of this study emphasize the critical role of the surface passivation of polycrystalline HfO2 dielectrics in improving the electrical performance of ultrathin In2O3 TFTs.

Mechanism of selective SiO2/photoresist reactive ion etching in an inductively coupled plasma operated in a C4F8/H2 gas mixture

A reactive ion etch process that achieves high selectivity between SiO2 and photoresist (PR) and based on C4F8/H2 chemistry in an inductively coupled radio frequency plasma is developed. The process is accompanied by the formation of a fluorocarbon film, which defines key process characteristics. The SiO2 etching is described as a sum of two competing mechanisms: (i) an inhibition mechanism related to fluorocarbon film deposition and (ii) a defluorination mechanism, describing the diffusion of etching species to the CxFy/SiO2 interface. However, the photoresist etch rate is primarily determined by the inhibition mechanism. In order to achieve high SiO2/PR selectivity, both mechanisms are studied as functions of hydrogen admixture, pressure, gas residence time, and substrate temperature. This study reveals that depending on the superposition of the process parameters, one of the mechanisms can prevail over the other one, which significantly affects etch rates and selectivity. By adjusting the process parameters, a maximum selectivity between SiO2 and PR of 8 is achieved corresponding to a SiO2 etch rate of 200 nm/min.

Single mode, distributed feedback interband cascade lasers grown on Si for gas sensing

A single mode distributed feedback (DFB) interband cascade laser (ICL) grown on a (001) Si substrate has been developed. The designed DFB ICL with a grating on top of the ridge emits at a wavelength near 3.4 μm, suited for methane gas sensing, and operates in continuous wave up to 35 °C, with a maximum output power of 4 mW/facet at 15 °C and a side mode suppression ratio of 20 dB in the whole operating range. Methane detection has been demonstrated by integrating the DFB ICL on Si with a quartz-enhanced photoacoustic spectroscopy setup, a step forward in the development of integrated photonic gas sensors on silicon platforms.