Anomalous elasticity of talc at high pressures:Implications for subduction systems

Talc is a layered hydrous silicate mineral that plays a vital role in transporting water into Earth’s interior and is crucial for explaining geophysical observations in subduction zone settings.In this study,we explored the structure,equation of state,and elasticity of both triclinic and monoclinic talc under high pressures up to 18 GPa using first principles simulations based on density functional theory corrected for dispersive forces.Our results indicate that principal components of the full elastic constant tensor C_(11) and C_(22),shear components C_(66),and several off-diagonal components show anomalous pressure dependence.This non-monotonic pressure dependence of elastic constant components is likely related to the structural changes and is often manifested in a polytypic transition from a low-pressure polytype talc-I to a high-pressure polytype talc-Ⅱ.The polytypic transition of talc occurs at pressures within its thermodynamic stability.However,the bulk and shear elastic moduli show no anomalous softening.Our study also shows that talc has low velocity,extremely high anisotropy,and anomalously high V_(P)/V_(S) ratio,thus making it a potential candidate mineral phase that could readily explain unusually high V_(P)/V_(S) ratio and large shear wave splitting delays as observed from seismological studies in many subduction systems.

Gravitational wave astrophysics, data analysis and multimessenger astronomy

This paper reviews gravitational wave sources and their detection. One of the most exciting potential sources of gravitational waves are coalescing binary black hole systems. They can occur on all mass scales and be formed in numerous ways, many of which are not understood. They are generally invisible in electromagnetic waves, and they provide opportunities for deep investigation of Einstein's general theory of relativity. Sect. 1 of this paper considers ways that binary black holes can be created in the universe, and includes the prediction that binary black hole coalescence events are likely to be the first gravitational wave sources to be detected. The next parts of this paper address the detection of chirp waveforms from coalescence events in noisy data.Such analysis is computationally intensive. Sect. 2 reviews a new and powerful method of signal detection based on the GPUimplemented summed parallel infinite impulse response filters. Such filters are intrinsically real time alorithms, that can be used to rapidly detect and localise signals. Sect. 3 of the paper reviews the use of GPU processors for rapid searching for gravitational wave bursts that can arise from black hole births and coalescences. In sect. 4 the use of GPU processors to enable fast efficient statistical significance testing of gravitational wave event candidates is reviewed. Sect. 5 of this paper addresses the method of multimessenger astronomy where the discovery of electromagnetic counterparts of gravitational wave events can be used to identify sources, understand their nature and obtain much greater science outcomes from each identified event.

Cluster structure prediction via CALYPSO method

Cluster science as a bridge linking atomic molecular physics and condensed matter inspired the nanomaterials development in the past decades, ranging from the single-atom catalysis to ligand-protected noble metal clusters. The corresponding studies not only have been restricted to the search for the geometrical structures of clusters, but also have promoted the development of cluster-assembled materials as the building blocks. The CALYPSO cluster prediction method combined with other computational techniques have significantly stimulated the development of the cluster-based nanomaterials. In this review, we will summarize some good cases of cluster structure by CALYPSO method, which have also been successfully identified by the photoelectron spectra experiments. Beginning with the alkali-metal clusters, which serve as benchmarks, a series of studies are performed on the size-dependent elemental clusters which possess relatively high stability and interesting chemical physical properties. Special attentions are paid to the boron-based clusters because of their promising applications. The NbSi12 and BeB16 clusters, for example, are two classic representatives of the silicon-and boron-based clusters, which can be viewed as building blocks of nanotubes and borophene. This review offers a detailed description of the structural evolutions and electronic properties of medium-sized pure and doped clusters, which will advance fundamental knowledge of cluster-based nanomaterials and provide valuable information for further theoretical and experimental studies.

Geoscience material structures prediction via CALYPSO methodology

Many properties of planets such as their interior structure and thermal evolution depend on the high-pressure properties of their constituent materials. This paper reviews how crystal structure prediction methodology can help shed light on the transformations materials undergo at the extreme conditions inside planets. The discussion focuses on three areas:(i) the propensity of iron to form compounds with volatile elements at planetary core conditions(important to understand the chemical makeup of Earth's inner core),(ii) the chemistry of mixtures of planetary ices(relevant for the mantle regions of giant icy planets), and(iii) examples of mantle minerals. In all cases the abilities and current limitations of crystal structure prediction are discussed across a range of example studies.

A modified Lin equation for the energy balance in isotropic turbulence

At sufficiently large Reynolds numbers,turbulence is expected to exhibit scale-invariance in an intermediate("inertial")range of wavenumbers,as shown by power law behavior of the energy spectrum and also by a constant rate of energy transfer through wavenumber.However,there is an apparent contradiction between the definition of the energy flux(i.e.,the integral of the transfer spectrum)and the observed behavior of the transfer spectrum itself.This is because the transfer spectrum T(k)is invariably found to have a zero-crossing at a single point(at k=k*),implying that the corresponding energy flux cannot have an extended plateau but must instead have a maximum value at k=k*.This behavior was formulated as a paradox and resolved by the introduction of filtered/partitioned transfer spectra,which exploited the symmetries of the triadic interactions(J.Phys.A:Math.Theor.,2008).In this paper we consider the more general implications of that procedure for the spectral energy balance equation,also known as the Lin equation.It is argued that the resulting modified Lin equations(and their corresponding Navier–Stokes equations)offer a new starting point for both numerical and theoretical methods,which may lead to a better understanding of the underlying energy transfer processes in turbulence.In particular the filtered partitioned transfer spectra could provide a basis for a hybrid approach to the statistical closure problem,with the different spectra being tackled using different methods.

Following up the afterglow:strategy for X-ray observation triggered by gravitational wave events

The multi-messenger observation of coalescing compact binary systems promises great scientific treasure.However,synthesising observations from both gravitational wave and electromagnetic channels remains challenging.In the context of the day-to-week long emission from a macronova,the binary neutron star merger GW170817 remains the only event with successful electromagnetic followup.In this manuscript,we explore the possibility of using the early stage X-ray afterglow to search for the electromagnetic counterpart of a gravitational wave event.Two algorithms,the simple and straightforward sequential observation(SO)and the step-wise optimizing local optimization are considered and applied to some simulated events.We consider the WXT from the proposed Einstein Probe as a candidate X-ray telescope,which has a very wide field of view of 3600 deg^(2).Benefiting from the large field of view and high sensitivity,we find that the SO algorithm not only is easy to implement,but also promises a good chance of actual detection.

Highly efficient organic light-emitting diodes and light-emitting electrochemical cells employing multiresonant thermally activated delayed fluorescent emitters with bulky donor or acceptor peripheral groups

Multiresonant thermally activated delayedfluorescence(MR-TADF)emitters have been the focus of extensive design efforts as they are recognized to show bright,narrowband emission,which makes them very appealing for display applications.However,the planar geometry and relatively large singlet–triplet energy gap lead to,respectively,severe aggregation-caused quenching(ACQ)and slow reverse intersys-tem crossing(RISC).Here,a design strategy is proposed to address both issues.Two MR-TADF emitters triphenylphosphine oxide(TPPO)-tBu-DiKTa and tripheny-lamine(TPA)-tBu-DiKTa have been synthesized.Twisted ortho-substituted groups help increase the intermolecular distance and largely suppress the ACQ.In addition,the contributions from intermolecular charge transfer states in the case of TPA-tBu-DiKTa help to accelerate RISC.The organic light-emitting diodes(OLEDs)with TPPO-tBu-DiKTa and TPA-tBu-DiKTa exhibit high maximum external quan-tum efficiencies(EQEmax)of 24.4%and 31.0%,respectively.Notably,the device with 25 wt%TPA-tBu-DiKTa showed both high EQEmax of 28.0%and reduced efficiency roll-off(19.9%EQE at 1000 cd m^(-2))compared to the device with 5 wt%emitter(31.0%EQEmax and 11.0%EQE at 1000 cd m^(-2)).The new emitters were also introduced into single-layer light-emitting electrochemical cells(LECs),equipped with air-stable electrodes.The LEC containing TPA-tBu-DiKTa dispersed at 0.5 wt%in a matrix comprising a mobility-balanced blend-host and an ionic liq-uid electrolyte delivered blue luminance with an EQEmax of 2.6%at 425 cd m^(-2).The high efficiencies of the OLEDs and LECs with TPA-tBu-DiKTa illustrate the potential for improving device performance when the DiKTa core is decorated with twisted bulky donors.

Light sheet microscope scanning of biointegrated microlasers for localized refractive index sensing

Whispering gallery mode(WGM)microlasers are highly sensitive to localized refractive index changes allowing to link their emission spectrum to various chemical,mechanical,or physical stimuli.Microlasers recently found applications in biological studies within single cells,in three-dimensional samples such as multicellular spheroids,or in vivo.However,detailed studies of biological samples also need to account for the structural heterogeneity of tissues and live animals,therefore requiring a combination of high-resolution microscopy and laser spectroscopy.Here,we design and construct a light sheet fluorescence microscope with a coupled spectrometer for use in microlaser studies for combined high-resolution,high-speed imaging and WGM spectral analysis.The light sheet illumination profile and the decoupled geometry of excitation and emission hereby directly affect the lasing and sensing properties,mainly through geometric constraints and by light coupling effects.We demonstrate the basic working principle of microlaser spectroscopy under light sheet excitation and measure the absolute refractive index within agarose and in zebrafish tail muscle tissue.We further analyze the light coupling conditions that lead to the occurrence of two separate oscillation planes.These so-called cross modes can be scanned around the entire microlaser surface,which allows to estimate a surface-averaged refractive index profile of the microlaser environment.

Organic photovoltaics for simultaneous energy harvesting and high-speed MIMO optical wireless communications

We show that organic photovoltaics(OPVs)are suitable for high-speed optical wireless data receivers that can also harvest power.In addition,these OPVs are of particular interest for indoor applications,as their bandgap is larger than that of silicon,leading to better matching to the spectrum of artificial light.By selecting a suitable combination of a narrow bandgap donor polymer and a nonfullerene acceptor,stable OPVs are fabricated with a power conversion efficiency of 8.8%under 1 Sun and 14%under indoor lighting conditions.In an optical wireless communication experiment,a data rate of 363 Mb/s and a simultaneous harvested power of 10.9 mW are achieved in a 4-by-4 multipleinput multiple-output(MIMO)setup that consists of four laser diodes,each transmitting 56 mW optical power and four OPV cells on a single panel as receivers at a distance of 40 cm.This result is the highest reported data rate using OPVs as data receivers and energy harvesters.This finding may be relevant to future mobile communication applications because it enables enhanced wireless data communication performance while prolonging the battery life in a mobile device.

Quantum-optical spectroscopy of a twolevel system using an electrically driven micropillar laser as a resonant excitation source

Two-level emitters are the main building blocks of photonic quantum technologies and are model systems for the exploration of quantum optics in the solid state.Most interesting is the strict resonant excitation of such emitters to control their occupation coherently and to generate close to ideal quantum light,which is of utmost importance for applications in photonic quantum technology.To date,the approaches and experiments in this field have been performed exclusively using bulky lasers,which hinders the application of resonantly driven two-level emitters in compact photonic quantum systems.Here we address this issue and present a concept for a compact resonantly driven single-photon source by performing quantum-optical spectroscopy of a two-level system using a compact high-βmicrolaser as the excitation source.The two-level system is based on a semiconductor quantum dot(QD),which is excited resonantly by a fiber-coupled electrically driven micropillar laser.We dress the excitonic state of the QD under continuous wave excitation,and trigger the emission of single photons with strong multi-photon suppression(ge2Te0T?0:02)and high photon indistinguishability(V=57±9%)via pulsed resonant excitation at 156 MHz.These results clearly demonstrate the high potential of our resonant excitation scheme,which can pave the way for compact electrically driven quantum light sources with excellent quantum properties to enable the implementation of advanced quantum communication protocols.

Sharpening emitter localization in front of a tuned mirror

Single-molecule localization microscopy(SMLM)aims for maximized precision and a high signal-to-noise ratio1.Both features can be provided by placing the emitter in front of a metal-dielectric nanocoating that acts as a tuned mirror2–4.Here,we demonstrate that a higher photon yield at a lower background on biocompatible metal-dielectric nanocoatings substantially improves SMLM performance and increases the localization precision by up to a factor of two.The resolution improvement relies solely on easy-to-fabricate nanocoatings on standard glass coverslips and is spectrally and spatially tunable by the layer design and wavelength,as experimentally demonstrated for dual-color SMLM in cells.

Deformable microlaser force sensing

Mechanical forces are key regulators of cellular behavior and function,affecting many fundamental biological processes such as cell migration,embryogenesis,immunological responses,and pathological states.Specialized force sensors and imaging techniques have been developed to quantify these otherwise invisible forces in single cells and in vivo.However,current techniques rely heavily on high-resolution microscopy and do not allow interrogation of optically dense tissue,reducing their application to 2D cell cultures and highly transparent biological tissue.Here,we introduce DEFORM,deformable microlaser force sensing,a spectroscopic technique that detects sub-nanonewton forces with unprecedented spatio-temporal resolution.DEFORM is based on the spectral analysis of laser emission from dye-doped oil microdroplets and uses the force-induced lifting of laser mode degeneracy in these droplets to detect nanometer deformations.Following validation by atomic force microscopy and development of a model that links changes in laser spectrum to applied force,DEFORM is used to measure forces in 3D and at depths of hundreds of microns within tumor spheroids and late-stage Drosophila larva.We furthermore show continuous force sensing with single-cell spatial and millisecond temporal resolution,thus paving the way for non-invasive studies of biomechanical forces in advanced stages of embryogenesis,tissue remodeling,and tumor invasion.

Light-deformable microrobots shape up for the biological obstacle course

Euglena gracilis microalga has been transformed into a soft bio-microrobot with light-controlled motion and deformation that can address diverse bio-challenges,such as drug delivery,diseased cell removal,and photodynamic therapy.

A material change for ultra-high precision force sensing

An original form of photonic force microscope has been developed.Operating with a trapped lanthanide-doped crystal of nanometric dimensions,a minimum detected force of the order of 110 aN and a force sensitivity down to 1.8 fN/ffiffiffiffiffi Hz p have been realised.This opens up new prospects for force sensing in the physical sciences.

Nonlinear Rydberg exciton-polaritons in Cu2O microcavities

Rydberg excitons(analogues of Rydberg atoms in condensed matter systems)are highly excited bound electron-hole states with large Bohr radii.The interaction between them as well as exciton coupling to light may lead to strong optical nonlinearity,with applications in sensing and quantum information processing.Here,we achieve strong effective photon–photon interactions(Kerr-like optical nonlinearity)via the Rydberg blockade phenomenon and the hybridisation of excitons and photons forming polaritons in a Cu2O-filled microresonator.Under pulsed resonant excitation polariton resonance frequencies are renormalised due to the reduction of the photon-exciton coupling with increasing exciton density.Theoretical analysis shows that the Rydberg blockade plays a major role in the experimentally observed scaling of the polariton nonlinearity coefficient as∝n4.4±1.8 for principal quantum numbers up to n=7.Such high principal quantum numbers studied in a polariton system for the first time are essential for realisation of high Rydberg optical nonlinearities,which paves the way towards quantum optical applications and fundamental studies of strongly correlated photonic(polaritonic)states in a solid state system.

Optical trapping with structured light: a review

Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer.In the case of 3D trapping with a single beam,this is termed optical tweezers.Optical tweezers are a powerful and noninvasive tool for manipulating small objects,and have become indispensable in many fields,including physics,biology,soft condensed matter,among others.In the early days,optical trapping was typically accomplished with a single Gaussian beam.In recent years,we have witnessed rapid progress in the use of structured light beams with customized phase,amplitude,and polarization in optical trapping.Unusual beam properties,such as phase singularities on-axis and propagation invariant nature,have opened up novel capabilities to the study of micromanipulation in liquid,air,and vacuum.We summarize the recent advances in the field of optical trapping using structured light beams.

Zero-dimensional polariton laser in a subwavelength grating-based vertical microcavity

Semiconductor exciton–polaritons in planar microcavities form coherent two-dimensional condensates in non-equilibrium.However,the coupling of multiple lower-dimensional polariton quantum systems,which are critical for polaritonic quantum device applications and novel cavity-lattice physics,has been limited in conventional cavity structures.Here,we demonstrate full non-destructive confinement of polaritons using a hybrid cavity composed of a single-layer subwavelength grating mirror and a distributed Bragg reflector.Single-mode polariton lasing was observed at a chosen polarization.The incorporation of a designable slab mirror in a conventional vertical cavity,when operating in the strong-coupling regime,enables the confinement,control and coupling of polariton gasses in a scalable fashion.This approach may open the door to experimental implementations of polariton-based quantum photonic devices and coupled cavity quantum electrodynamic systems.

Triple-cation perovskite solar cells for visible light communications

Hybrid perovskite materials are widely researched due to their high absorptivity,inexpensive synthesis,and promise in photovoltaic devices.These materials are also of interest as highly sensitive photodetectors.In this study,their potential for use in visible light communication is explored in a configuration that allows for simultaneous energy and data harvesting.Using a triple-cation material and appropriate device design,a new record data rate for perovskite photodetectors of 56 Mbps and power conversion efficiencies above 20%under white LED illumination are achieved.With this device design,the−3 dB bandwidth is increased by minimizing the dominating time constant of the system.This correlation between the bandwidth and time constant is proved using measurements of time-resolved photoluminescence,transient photovoltage,and device resistance.

Spiniform phase-encoded metagratings entangling arbitrary rational-order orbital angular momentum

Quantum entanglements between integer-order and fractional-order orbital angular momentums(OAMs)have been previously discussed.However,the entangled nature of arbitrary rational-order OAM has long been considered a myth due to the absence of an effective strategy for generating arbitrary rational-order OAM beams.Therefore,we report a single metadevice comprising a bilaterally symmetric grating with an aperture,creating optical beams with dynamically controllable OAM values that are continuously varying over a rational range.Due to its encoded spiniform phase,this novel metagrating enables the production of an average OAM that can be increased without a theoretical limit by embracing distributed singularities,which differs significantly from the classic method of stacking phase singularities using fork gratings.This new method makes it possible to probe the unexplored niche of quantum entanglement between arbitrarily defined OAMs in light,which could lead to the complex manipulation of microparticles,high-dimensional quantum entanglement and optical communication.We show that quantum coincidence based on rational-order OAM-superposition states could give rise to low cross-talks between two different states that have no significant overlap in their spiral spectra.Additionally,future applications in quantum communication and optical micromanipulation may be found.

Experimentally unsupervised deconvolution for light-sheet microscopy with propagation-invariant beams

Deconvolution is a challenging inverse problem,particularly in techniques that employ complex engineered pointspread functions,such as microscopy with propagation-invariant beams.Here,we present a deep-learning method for deconvolution that,in lieu of end-to-end training with ground truths,is trained using known physics of the imaging system.Specifically,we train a generative adversarial network with images generated with the known point-spread function of the system,and combine this with unpaired experimental data that preserve perceptual content.Our method rapidly and robustly deconvolves and super-resolves microscopy images,demonstrating a two-fold improvement in image contrast to conventional deconvolution methods.In contrast to common end-to-end networks that often require 1000-10,000s paired images,our method is experimentally unsupervised and can be trained solely on a few hundred regions of interest.We demonstrate its performance on light-sheet microscopy with propagation-invariant Airy beams in oocytes,preimplantation embryos and excised brain tissue,as well as illustrate its utility for Bessel-beam LSM.This method aims to democratise learned methods for deconvolution,as it does not require data acquisition outwith the conventional imaging protocol.