Neural representations arise from high-dimensional population activity,but current neuromodulation methods lack the precision to write information into the central nervous system at this complexity.In this perspective...Neural representations arise from high-dimensional population activity,but current neuromodulation methods lack the precision to write information into the central nervous system at this complexity.In this perspective,we propose high-dimensional stimulation as an approach to better approximate natural neural codes for brain-machine interfaces.Key advancements in resolution,coverage,and safety are essential,with flexible microelectrode arrays offering a promising path toward precise synthetic neural codes.展开更多
Super-resolution microscopy has revolutionized our ability to visualize structures below the diffraction limit of conventional optical microscopy and is particularly useful for investigating complex biological targets...Super-resolution microscopy has revolutionized our ability to visualize structures below the diffraction limit of conventional optical microscopy and is particularly useful for investigating complex biological targets like chromatin.Chromatin exhibits a hierarchical organization with structural compartments and domains at different length scales,from nanometers to micrometers.Single molecule localization microscopy(SMLM)methods,such as STORM,are essential for studying chromatin at the supra-nucleosome level due to their ability to target epigenetic marks that determine chromatin organization.Multi-label imaging of chromatin is necessary to unpack its structural complexity.However,these efforts are challenged by the high-density nuclear environment,which can affect antibody binding affinities,diffusivity and non-specific interactions.Optimizing buffer conditions,fluorophore stability,and antibody specificity is crucial for achieving effective antibody conjugates.Here,we demonstrate a sequential immunolabeling protocol that reliably enables three-color studies within the dense nuclear environment.This protocol couples multiplexed localization datasets with a robust analysis algorithm,which utilizes localizations from one target as seed points for distance,density and multi-label joint affinity measurements to explore complex organization of all three targets.Applying this multiplexed algorithm to analyze distance and joint density reveals that heterochromatin and euchromatin are not-distinct territories,but that localization of transcription and euchromatin couple with the periphery of heterochromatic clusters.This work is a crucial step in molecular imaging of the dense nuclear environment as multi-label capacity enables for investigation of complex multi-component systems like chromatin with enhanced accuracy.展开更多
Hydrogels can improve the delivery of mesenchymal stromal cells(MSCs)by providing crucial biophysical cues that mimic the extracellular matrix.The differentiation of MSCs is dependent on biophysical cues like stiffnes...Hydrogels can improve the delivery of mesenchymal stromal cells(MSCs)by providing crucial biophysical cues that mimic the extracellular matrix.The differentiation of MSCs is dependent on biophysical cues like stiffness and viscoelasticity,yet conventional hydrogels cannot be dynamically altered after fabrication and implantation to actively direct differentiation.We developed a composite hydrogel,consisting of type I collagen and phase-shift emulsion,where osteogenic differentiation of MSCs can be non-invasively modulated using ultrasound.When exposed to ultrasound,the emulsion within the hydrogel was non-thermally vaporized into bubbles,which locally compacted and stiffened the collagen matrix surrounding each bubble.Bubble growth and matrix compaction were correlated,with collagen regions proximal(i.e.,≤~60μm)to the bubble displaying a 2.5-fold increase in Young’s modulus compared to distal regions(i.e.,>~60μm).The viability and proliferation of MSCs,which were encapsulated within the composite hydrogel,were not impacted by bubble formation.In vitro and in vivo studies revealed encapsulated MSCs exhibited significantly elevated levels of RUNX2 and osteocalcin,markers of osteogenic differentiation,in collagen regions proximal to the bubble compared to distal regions.Additionally,alkaline phosphatase activity and calcium deposition were enhanced adjacent to the bubble.An opposite trend was observed for CD90,a marker of MSC stemness.Following subcutaneous implantation,bubbles persisted in the hydrogels for two weeks,which led to localized collagen alignment and increases in nuclear asymmetry.These results are a significant step toward controlling the 3D differentiation of MSCs in a noninvasive and on-demand manner.展开更多
Wavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical field.Traditional wavefront sensors such as Shack-Hartmann wavefront sensor(SHWFS)suffer from a fundamental tradeoff ...Wavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical field.Traditional wavefront sensors such as Shack-Hartmann wavefront sensor(SHWFS)suffer from a fundamental tradeoff between spatial resolution and phase estimation and consequently can only achieve a resolution of a few thousand pixels.To break this tradeoff,we present a novel computational-imaging-based technique,namely,the Wavefront Imaging Sensor with High resolution(WISH).We replace the microlens array in SHWFS with a spatial light modulator(SLM)and use a computational phase-retrieval algorithm to recover the incident wavefront.This wavefront sensor can measure highly varying optical fields at more than 10-megapixel resolution with the fine phase estimation.To the best of our knowledge,this resolution is an order of magnitude higher than the current noninterferometric wavefront sensors.To demonstrate the capability of WISH,we present three applications,which cover a wide range of spatial scales.First,we produce the diffraction-limited reconstruction for long-distance imaging by combining WISH with a large-aperture,low-quality Fresnel lens.Second,we show the recovery of high-resolution images of objects that are obscured by scattering.Third,we show that WISH can be used as a microscope without an objective lens.Our study suggests that the designing principle of WISH,which combines optical modulators and computational algorithms to sense high-resolution optical fields,enables improved capabilities in many existing applications while revealing entirely new,hitherto unexplored application areas.展开更多
High-intensity laser–plasma interactions produce a wide array of energetic particles and beams with promising applications.Unfortunately,the high repetition rate and high average power requirements for many applicati...High-intensity laser–plasma interactions produce a wide array of energetic particles and beams with promising applications.Unfortunately,the high repetition rate and high average power requirements for many applications are not satisfied by the lasers,optics,targets,and diagnostics currently employed.Here,we aim to address the need for high-repetition-rate targets and optics through the use of liquids.A novel nozzle assembly is used to generate highvelocity,laminar-flowing liquid microjets which are compatible with a low-vacuum environment,generate little to no debris,and exhibit precise positional and dimensional tolerances.Jets,droplets,submicron-thick sheets,and other exotic configurations are characterized with pump–probe shadowgraphy to evaluate their use as targets.To demonstrate a highrepetition-rate,consumable,liquid optical element,we present a plasma mirror created by a submicron-thick liquid sheet.This plasma mirror provides etalon-like anti-reflection properties in the low field of 0.1%and high reflectivity as a plasma,69%,at a repetition rate of 1 k Hz.Practical considerations of fluid compatibility,in-vacuum operation,and estimates of maximum repetition rate are addressed.The targets and optics presented here demonstrate a potential technique for enabling the operation of laser–plasma interactions at high repetition rates.展开更多
This report concerns a benchtop prototype instrument containing a gas chromatographic microanalytical system(μGC)designed for the selective determination of multiple airborne volatile organic compounds(VOCs)at concen...This report concerns a benchtop prototype instrument containing a gas chromatographic microanalytical system(μGC)designed for the selective determination of multiple airborne volatile organic compounds(VOCs)at concentrations in the vicinity of recommended occupational exposure limits.The core microsystem consists of a set of discrete Si-microfabricated devices:a dualcavity,adsorbent-packed micro-preconcentrator-focuser(μPCF)chip that quantitatively captures and thermally desorbs/injects VOCs with vapor pressures between~0.03 and 13 kPa;tandem micro-column(μcolumn)chips with cross-linked PDMS wall-coated stationary phases capable of temperature-programmed separations;and an integrated array of fiveμchemiresistors(μCR)coated with different thiolate-monolayer protected gold nanoparticle(MPN)interface films that quantifies and further differentiates among the analytes by virtue of the response patterns generated.Other key components include a pre-trap for low-volatility interferences,a split-flow injection valve,and an onboard He carrier–gas canister.The assembled unit measures 19×30×14 cm,weighs~3.5 kg,operates on AC power,and is laptop/LabVIEW controlled.Component-and system-level tests of performance demonstrated injection bandwidths o1 s,aμcolumn capacity of≥8μg injected mass,linear calibration curves,no humidity effects,excellent medium-term(that is,1 week)reproducibility,autonomous operation for 8 h,detection limits below Threshold Limit Values(TLV)for 10 mL air samples collected in 1 min,and response patterns that enhanced vapor recognition.The determination of a 17-VOC mixture in the presence of seven interferences was performed in 4 min.Results augur well for adapting the microsystem to an all-MEMS wearableμGC currently under parallel development.展开更多
Efforts to map atomic-scale chemistry at low doses with minimal noise using electron microscopes are fundamentally limited by inelastic interactions.Here,fused multi-modal electron microscopy offers high signal-to-noi...Efforts to map atomic-scale chemistry at low doses with minimal noise using electron microscopes are fundamentally limited by inelastic interactions.Here,fused multi-modal electron microscopy offers high signal-to-noise ratio(SNR)recovery of material chemistry at nano-and atomic-resolution by coupling correlated information encoded within both elastic scattering(high-angle annular dark-field(HAADF))and inelastic spectroscopic signals(electron energy loss(EELS)or energy-dispersive x-ray(EDX)).By linking these simultaneously acquired signals,or modalities,the chemical distribution within nanomaterials can be imaged at significantly lower doses with existing detector hardware.In many cases,the dose requirements can be reduced by over one order of magnitude.This high SNR recovery of chemistry is tested against simulated and experimental atomic resolution data of heterogeneous nanomaterials.展开更多
Carbon nanotubes are explored as a means of coherently converting the orbital angular momentum of light to an excitonic form that is more amenable to quantum information processing.An analytical analysis,based on dyna...Carbon nanotubes are explored as a means of coherently converting the orbital angular momentum of light to an excitonic form that is more amenable to quantum information processing.An analytical analysis,based on dynamical conductivity,is used to show that orbital angular momentum is conserved,modulo N,for a carbon nanotube illuminated by radially polarized,twisted light.This result is numerically demonstrated using real-time time-dependent density functional theory which captures the absorption of twisted light and the subsequent transfer of twisted excitons.The results suggest that carbon nanotubes are promising candidates for constructing optoelectronic circuits in which quantum information is more readily processed while manifested in excitonic form.展开更多
Excitons,bound electron–hole pairs,in two-dimensional hybrid organic inorganic perovskites(2D HOIPs)are capable of forming hybrid light-matter states known as exciton-polaritons(E–Ps)when the excitonic medium is con...Excitons,bound electron–hole pairs,in two-dimensional hybrid organic inorganic perovskites(2D HOIPs)are capable of forming hybrid light-matter states known as exciton-polaritons(E–Ps)when the excitonic medium is confined in an optical cavity.In the case of 2D HOIPs,they can self-hybridize into E–Ps at specific thicknesses of the HOIP crystals that form a resonant optical cavity with the excitons.However,the fundamental properties of these self-hybridized E–Ps in 2D HOIPs,including their role in ultrafast energy and/or charge transfer at interfaces,remain unclear.Here,we demonstrate that>0.5µm thick 2D HOIP crystals on Au substrates are capable of supporting multiple-orders of self-hybridized E–P modes.These E–Ps have high Q factors(>100)and modulate the optical dispersion for the crystal to enhance sub-gap absorption and emission.Through varying excitation energy and ultrafast measurements,we also confirm energy transfer from higher energy E–Ps to lower energy E–Ps.Finally,we also demonstrate that E–Ps are capable of charge transport and transfer at interfaces.Our findings provide new insights into charge and energy transfer in E–Ps opening new opportunities towards their manipulation for polaritonic devices.展开更多
The manipulation and control of nanoscale magnetic spin textures are of rising interest as they are potential foundational units in next-generation computing paradigms.Achieving this requires a quantitative understand...The manipulation and control of nanoscale magnetic spin textures are of rising interest as they are potential foundational units in next-generation computing paradigms.Achieving this requires a quantitative understanding of the spin texture behavior under external stimuli using in situ experiments.Lorentz transmission electron microscopy(LTEM)enables real-space imaging of spin textures at the nanoscale,but quantitative characterization of in situ data is extremely challenging.Here,we present an AI-enabled phase-retrieval method based on integrating a generative deep image prior with an image formation forwardmodel for LTEM.Our approach uses a single out-of-focus image for phase retrieval and achieves significantly higher accuracy and robustness to noise compared to existing methods.Furthermore,our method is capable of isolating sample heterogeneities from magnetic contrast,as shown by application to simulated and experimental data.This approach allows quantitative phase reconstruction of in situ data and can also enable near real-time quantitative magnetic imaging.展开更多
Recent interest in developing fast spintronic devices and laser-controllable magnetic solids has sparked tremendous experimental and theoretical efforts to understand and manipulate ultrafast dynamics in materials.Stu...Recent interest in developing fast spintronic devices and laser-controllable magnetic solids has sparked tremendous experimental and theoretical efforts to understand and manipulate ultrafast dynamics in materials.Studies of spin dynamics in the terahertz(THz)frequency range are particularly important for elucidating microscopic pathways toward novel device functionalities.Here,we review THz phenomena related to spin dynamics in rare-earth orthoferrites,a class of materials promising for antiferromagnetic spintronics.We expand this topic into a description of four key elements.(1)We start by describing THz spectroscopy of spin excitations for probing magnetic phase transitions in thermal equilibrium.While acoustic magnons are useful indicators of spin reorientation transitions,electromagnons that arise from dynamic magnetoelectric couplings serve as a signature of inversion-symmetry-breaking phases at low temperatures.(2)We then review the strong laser driving scenario,where the system is excited far from equilibrium and thereby subject to modifications to the free-energy landscape.Microscopic pathways for ultrafast laser manipulation of magnetic order are discussed.(3)Furthermore,we review a variety of protocols to manipulate coherent THz magnons in time and space,which are useful capabilities for antiferromagnetic spintronic applications.(4)Finally,new insights into the connection between dynamic magnetic coupling in condensed matter and the Dicke superradiant phase transition in quantum optics are provided.By presenting a review on an array of THz spin phenomena occurring in a single class of materials,we hope to trigger interdisciplinary efforts that actively seek connections between subfields of spintronics,which will facilitate the invention of new protocols of active spin control and quantum phase engineering.展开更多
基金funded by R01EY036094(L.L)R01NS102917(C.X)+1 种基金U01NS115588(C.X)U01NS131086(C.X&L.L.)。
文摘Neural representations arise from high-dimensional population activity,but current neuromodulation methods lack the precision to write information into the central nervous system at this complexity.In this perspective,we propose high-dimensional stimulation as an approach to better approximate natural neural codes for brain-machine interfaces.Key advancements in resolution,coverage,and safety are essential,with flexible microelectrode arrays offering a promising path toward precise synthetic neural codes.
基金supported by NIH grants U54CA268084,U54CA261694,and R01CA228272National Science Foundation grants EFMA-1830961 and CBET-2430743+1 种基金philanthropic support from Rob and Kristin Goldman,Mr.David Sachsthe Christina Carinato Charitable Foundation.
文摘Super-resolution microscopy has revolutionized our ability to visualize structures below the diffraction limit of conventional optical microscopy and is particularly useful for investigating complex biological targets like chromatin.Chromatin exhibits a hierarchical organization with structural compartments and domains at different length scales,from nanometers to micrometers.Single molecule localization microscopy(SMLM)methods,such as STORM,are essential for studying chromatin at the supra-nucleosome level due to their ability to target epigenetic marks that determine chromatin organization.Multi-label imaging of chromatin is necessary to unpack its structural complexity.However,these efforts are challenged by the high-density nuclear environment,which can affect antibody binding affinities,diffusivity and non-specific interactions.Optimizing buffer conditions,fluorophore stability,and antibody specificity is crucial for achieving effective antibody conjugates.Here,we demonstrate a sequential immunolabeling protocol that reliably enables three-color studies within the dense nuclear environment.This protocol couples multiplexed localization datasets with a robust analysis algorithm,which utilizes localizations from one target as seed points for distance,density and multi-label joint affinity measurements to explore complex organization of all three targets.Applying this multiplexed algorithm to analyze distance and joint density reveals that heterochromatin and euchromatin are not-distinct territories,but that localization of transcription and euchromatin couple with the periphery of heterochromatic clusters.This work is a crucial step in molecular imaging of the dense nuclear environment as multi-label capacity enables for investigation of complex multi-component systems like chromatin with enhanced accuracy.
基金supported by the Focused Ultrasound Foundation and NIH grant R01HL139656。
文摘Hydrogels can improve the delivery of mesenchymal stromal cells(MSCs)by providing crucial biophysical cues that mimic the extracellular matrix.The differentiation of MSCs is dependent on biophysical cues like stiffness and viscoelasticity,yet conventional hydrogels cannot be dynamically altered after fabrication and implantation to actively direct differentiation.We developed a composite hydrogel,consisting of type I collagen and phase-shift emulsion,where osteogenic differentiation of MSCs can be non-invasively modulated using ultrasound.When exposed to ultrasound,the emulsion within the hydrogel was non-thermally vaporized into bubbles,which locally compacted and stiffened the collagen matrix surrounding each bubble.Bubble growth and matrix compaction were correlated,with collagen regions proximal(i.e.,≤~60μm)to the bubble displaying a 2.5-fold increase in Young’s modulus compared to distal regions(i.e.,>~60μm).The viability and proliferation of MSCs,which were encapsulated within the composite hydrogel,were not impacted by bubble formation.In vitro and in vivo studies revealed encapsulated MSCs exhibited significantly elevated levels of RUNX2 and osteocalcin,markers of osteogenic differentiation,in collagen regions proximal to the bubble compared to distal regions.Additionally,alkaline phosphatase activity and calcium deposition were enhanced adjacent to the bubble.An opposite trend was observed for CD90,a marker of MSC stemness.Following subcutaneous implantation,bubbles persisted in the hydrogels for two weeks,which led to localized collagen alignment and increases in nuclear asymmetry.These results are a significant step toward controlling the 3D differentiation of MSCs in a noninvasive and on-demand manner.
基金supported in part by NSF CAREER grant IIS-1652633NSF grant IIS-1730574+1 种基金DARPA REVEAL grant HR0011-16-C-0028DARPA NESD program HR0011-17-C-0026.
文摘Wavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical field.Traditional wavefront sensors such as Shack-Hartmann wavefront sensor(SHWFS)suffer from a fundamental tradeoff between spatial resolution and phase estimation and consequently can only achieve a resolution of a few thousand pixels.To break this tradeoff,we present a novel computational-imaging-based technique,namely,the Wavefront Imaging Sensor with High resolution(WISH).We replace the microlens array in SHWFS with a spatial light modulator(SLM)and use a computational phase-retrieval algorithm to recover the incident wavefront.This wavefront sensor can measure highly varying optical fields at more than 10-megapixel resolution with the fine phase estimation.To the best of our knowledge,this resolution is an order of magnitude higher than the current noninterferometric wavefront sensors.To demonstrate the capability of WISH,we present three applications,which cover a wide range of spatial scales.First,we produce the diffraction-limited reconstruction for long-distance imaging by combining WISH with a large-aperture,low-quality Fresnel lens.Second,we show the recovery of high-resolution images of objects that are obscured by scattering.Third,we show that WISH can be used as a microscope without an objective lens.Our study suggests that the designing principle of WISH,which combines optical modulators and computational algorithms to sense high-resolution optical fields,enables improved capabilities in many existing applications while revealing entirely new,hitherto unexplored application areas.
基金supported by the Air Force Office of Scientific Research under LRIR Project 17RQCOR504 under the management of Dr. Riq Parraprovided by the AFOSR summer faculty program
文摘High-intensity laser–plasma interactions produce a wide array of energetic particles and beams with promising applications.Unfortunately,the high repetition rate and high average power requirements for many applications are not satisfied by the lasers,optics,targets,and diagnostics currently employed.Here,we aim to address the need for high-repetition-rate targets and optics through the use of liquids.A novel nozzle assembly is used to generate highvelocity,laminar-flowing liquid microjets which are compatible with a low-vacuum environment,generate little to no debris,and exhibit precise positional and dimensional tolerances.Jets,droplets,submicron-thick sheets,and other exotic configurations are characterized with pump–probe shadowgraphy to evaluate their use as targets.To demonstrate a highrepetition-rate,consumable,liquid optical element,we present a plasma mirror created by a submicron-thick liquid sheet.This plasma mirror provides etalon-like anti-reflection properties in the low field of 0.1%and high reflectivity as a plasma,69%,at a repetition rate of 1 k Hz.Practical considerations of fluid compatibility,in-vacuum operation,and estimates of maximum repetition rate are addressed.The targets and optics presented here demonstrate a potential technique for enabling the operation of laser–plasma interactions at high repetition rates.
基金Funding was provided by the National Institute for Occupational Safety and Health of the Centers for Disease Control and Prevention(Grant.R01-OH-010297).
文摘This report concerns a benchtop prototype instrument containing a gas chromatographic microanalytical system(μGC)designed for the selective determination of multiple airborne volatile organic compounds(VOCs)at concentrations in the vicinity of recommended occupational exposure limits.The core microsystem consists of a set of discrete Si-microfabricated devices:a dualcavity,adsorbent-packed micro-preconcentrator-focuser(μPCF)chip that quantitatively captures and thermally desorbs/injects VOCs with vapor pressures between~0.03 and 13 kPa;tandem micro-column(μcolumn)chips with cross-linked PDMS wall-coated stationary phases capable of temperature-programmed separations;and an integrated array of fiveμchemiresistors(μCR)coated with different thiolate-monolayer protected gold nanoparticle(MPN)interface films that quantifies and further differentiates among the analytes by virtue of the response patterns generated.Other key components include a pre-trap for low-volatility interferences,a split-flow injection valve,and an onboard He carrier–gas canister.The assembled unit measures 19×30×14 cm,weighs~3.5 kg,operates on AC power,and is laptop/LabVIEW controlled.Component-and system-level tests of performance demonstrated injection bandwidths o1 s,aμcolumn capacity of≥8μg injected mass,linear calibration curves,no humidity effects,excellent medium-term(that is,1 week)reproducibility,autonomous operation for 8 h,detection limits below Threshold Limit Values(TLV)for 10 mL air samples collected in 1 min,and response patterns that enhanced vapor recognition.The determination of a 17-VOC mixture in the presence of seven interferences was performed in 4 min.Results augur well for adapting the microsystem to an all-MEMS wearableμGC currently under parallel development.
基金R.H.and J.S.acknowledge support from the Army Research Office,Computing Sciences(W911NF-17-S-0002)and Dow Chemical CompanyWork at the Molecular Foundry was supported by the Office of Basic Energy Sciences,of the U.S.Department of Energy under Contract no.DE-AC02-05CH11231.
文摘Efforts to map atomic-scale chemistry at low doses with minimal noise using electron microscopes are fundamentally limited by inelastic interactions.Here,fused multi-modal electron microscopy offers high signal-to-noise ratio(SNR)recovery of material chemistry at nano-and atomic-resolution by coupling correlated information encoded within both elastic scattering(high-angle annular dark-field(HAADF))and inelastic spectroscopic signals(electron energy loss(EELS)or energy-dispersive x-ray(EDX)).By linking these simultaneously acquired signals,or modalities,the chemical distribution within nanomaterials can be imaged at significantly lower doses with existing detector hardware.In many cases,the dose requirements can be reduced by over one order of magnitude.This high SNR recovery of chemistry is tested against simulated and experimental atomic resolution data of heterogeneous nanomaterials.
基金The research reported in this publication was supported by funding from King Abdullah University of Science and Technology(KAUST).
文摘Carbon nanotubes are explored as a means of coherently converting the orbital angular momentum of light to an excitonic form that is more amenable to quantum information processing.An analytical analysis,based on dynamical conductivity,is used to show that orbital angular momentum is conserved,modulo N,for a carbon nanotube illuminated by radially polarized,twisted light.This result is numerically demonstrated using real-time time-dependent density functional theory which captures the absorption of twisted light and the subsequent transfer of twisted excitons.The results suggest that carbon nanotubes are promising candidates for constructing optoelectronic circuits in which quantum information is more readily processed while manifested in excitonic form.
基金support for this work by the Asian Office of Aerospace Research and Development of the Air Force Office of Scientific Research(AFOSR)FA2386-20-1-4074partial support from Office of Naval Research(ONR)Young Investigator Award(YIP)(N00014-23-1-203)+7 种基金S.B.A.gratefully acknowledges funding received from the Swiss National Science Foundation(SNSF)under the Early Postdoc Mobility grant(P2ELP2_187977)for this workC.M.is supported by an NSF-AFRL Intern Program.The experiments were carried out at the Singh Center for Nanotechnology at the University of Pennsylvania,which is supported by the National Science Foundation(N.S.F.)National Nanotechnology Coordinated Infrastructure Program grant NNCI-1542153D.J.and K.L.acknowledge the NSF REU SUNFEST program under Grant No.1950720,to support the stay of K.L.at the University of PennsylvaniaThe research performed by C.E.S.at the Air Force Research Laboratory was supported by contract award FA807518D0015J.R.H.acknowledges support from the Air Force Office of Scientific Research(Program Manager Dr.Gernot Pomrenke)under award number FA9550-20RYCOR059T.D.and P.J.S.gratefully acknowledge support from Programmable Quantum Materials,an Energy Frontier Research Center funded by the U.S.Department of Energy(DOE),Office of Science,Basic Energy Sciences(BES),under award DE-SC0019443H.H.acknowledges support from the Department of Energy(DE-SC0020101)A.D.M.acknowledges support from the Army Research Office(grant W911NF2210158).
文摘Excitons,bound electron–hole pairs,in two-dimensional hybrid organic inorganic perovskites(2D HOIPs)are capable of forming hybrid light-matter states known as exciton-polaritons(E–Ps)when the excitonic medium is confined in an optical cavity.In the case of 2D HOIPs,they can self-hybridize into E–Ps at specific thicknesses of the HOIP crystals that form a resonant optical cavity with the excitons.However,the fundamental properties of these self-hybridized E–Ps in 2D HOIPs,including their role in ultrafast energy and/or charge transfer at interfaces,remain unclear.Here,we demonstrate that>0.5µm thick 2D HOIP crystals on Au substrates are capable of supporting multiple-orders of self-hybridized E–P modes.These E–Ps have high Q factors(>100)and modulate the optical dispersion for the crystal to enhance sub-gap absorption and emission.Through varying excitation energy and ultrafast measurements,we also confirm energy transfer from higher energy E–Ps to lower energy E–Ps.Finally,we also demonstrate that E–Ps are capable of charge transport and transfer at interfaces.Our findings provide new insights into charge and energy transfer in E–Ps opening new opportunities towards their manipulation for polaritonic devices.
基金supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Materials Sciences and Engineering Divisionsupported by the U.S.Department of Energy,Office of Science,under Contract No.DE-AC02-06CH11357M.J.C also acknowledges support from Argonne LDRD 2021-0090-AutoPtycho:Autonomous,Sparse-sampled Ptychographic Imaging.
文摘The manipulation and control of nanoscale magnetic spin textures are of rising interest as they are potential foundational units in next-generation computing paradigms.Achieving this requires a quantitative understanding of the spin texture behavior under external stimuli using in situ experiments.Lorentz transmission electron microscopy(LTEM)enables real-space imaging of spin textures at the nanoscale,but quantitative characterization of in situ data is extremely challenging.Here,we present an AI-enabled phase-retrieval method based on integrating a generative deep image prior with an image formation forwardmodel for LTEM.Our approach uses a single out-of-focus image for phase retrieval and achieves significantly higher accuracy and robustness to noise compared to existing methods.Furthermore,our method is capable of isolating sample heterogeneities from magnetic contrast,as shown by application to simulated and experimental data.This approach allows quantitative phase reconstruction of in situ data and can also enable near real-time quantitative magnetic imaging.
基金X.L.acknowledges support from the Caltech Postdoctoral Prize Fellowship and the Institute for Quantum Information and Matter(IQIM).J.K.acknowledges support from the Robert A.Welch Foundation through Grant No.C-1509 and the U.S.Army Research Office through Grant No.W911NF-17-1-0259.
文摘Recent interest in developing fast spintronic devices and laser-controllable magnetic solids has sparked tremendous experimental and theoretical efforts to understand and manipulate ultrafast dynamics in materials.Studies of spin dynamics in the terahertz(THz)frequency range are particularly important for elucidating microscopic pathways toward novel device functionalities.Here,we review THz phenomena related to spin dynamics in rare-earth orthoferrites,a class of materials promising for antiferromagnetic spintronics.We expand this topic into a description of four key elements.(1)We start by describing THz spectroscopy of spin excitations for probing magnetic phase transitions in thermal equilibrium.While acoustic magnons are useful indicators of spin reorientation transitions,electromagnons that arise from dynamic magnetoelectric couplings serve as a signature of inversion-symmetry-breaking phases at low temperatures.(2)We then review the strong laser driving scenario,where the system is excited far from equilibrium and thereby subject to modifications to the free-energy landscape.Microscopic pathways for ultrafast laser manipulation of magnetic order are discussed.(3)Furthermore,we review a variety of protocols to manipulate coherent THz magnons in time and space,which are useful capabilities for antiferromagnetic spintronic applications.(4)Finally,new insights into the connection between dynamic magnetic coupling in condensed matter and the Dicke superradiant phase transition in quantum optics are provided.By presenting a review on an array of THz spin phenomena occurring in a single class of materials,we hope to trigger interdisciplinary efforts that actively seek connections between subfields of spintronics,which will facilitate the invention of new protocols of active spin control and quantum phase engineering.
