The discovery of ferromagnetic two-dimensional(2D)van der Waals(vdWs)materials provides an opportunity to explore intriguing physics and to develop innovative spin electronic devices.However,the main challenge for pra...The discovery of ferromagnetic two-dimensional(2D)van der Waals(vdWs)materials provides an opportunity to explore intriguing physics and to develop innovative spin electronic devices.However,the main challenge for practical applications of vd Ws ferromagnetic crystals lies in the weak intrinsic ferromagnetism and small perpendicular magnetic anisotropy(PMA)above room temperature.Here,we report the intrinsic vd Ws ferromagnetic crystal Fe_(3)GaTe_(2),synthesized by the self-flux method,exhibiting a Curie temperature(TC)of 370 K,a high saturation magnetization of 33.47 emu/g,and a large PMA energy density of approximately 4.17×10^(5)J/m^(3).Furthermore,the magneto-optical effect is systematically investigated in Fe_(3)GaTe_(2).The doubly degenerate E_(2g)(Γ)mode reverses the helicity of incident photons,indicating the existence of pseudoangular-momentum(PAM)and chirality.Meanwhile,the non-degenerate non-chiral A_(1g)(Γ)phonon exhibits a significant magneto-Raman effect under an external out-of-plane magnetic field.These results lay the groundwork for studying phonon chirality and magneto-optical phenomena in 2D magnetic materials,providing the feasibility for further fundamental research and applications in spintronic devices.展开更多
The emergent van der Waals magnetic material is a promising component for spintronic devices with novel functionalities.Here,we report a transition of negative-to-positive magnetoresistance in Fe_(3)GeTe_(2)/Cr_(2)Ge_...The emergent van der Waals magnetic material is a promising component for spintronic devices with novel functionalities.Here,we report a transition of negative-to-positive magnetoresistance in Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)van der Waals all-magnetic tunnel junctions with increasing the applied bias voltage.A negative magnetoresistance is observed first in Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)tunnel junctions,where the resistance with antiparallel aligned magnetization of two Fe_(3)GeTe_(2)electrodes is lower than that with parallel alignment,which is due to the opposite spin polarizations of two Fe_(3)GeTe_(2)electrodes.With the bias voltage increasing,the spin polarization of the biased Fe_(3)GeTe_(2)electrode is changed so that the spin orientations of two Fe_(3)GeTe_(2)electrodes are the same.Our experimental observations are supported by the calculated spin-dependent density of states for Fe_(3)GeTe_(2)electrodes under a finite bias.The significantly bias voltage-dependent spin transport properties in van der Waals magnetic tunnel junctions open a promising route for designing electrical controllable spintronic devices based on van der Waals magnets.展开更多
Two-dimensional(2D) atomic crystals,such as graphene,black phosphorus(BP) and transition metal dichalcogenides(TMDCs) are attractive for use in optoelectronic devices,due to their unique crystal structures and optical...Two-dimensional(2D) atomic crystals,such as graphene,black phosphorus(BP) and transition metal dichalcogenides(TMDCs) are attractive for use in optoelectronic devices,due to their unique crystal structures and optical absorption properties.In this study,we fabricated BP/ReS2 van der Waals(vdWs) heterojunction devices.The devices realized broadband photoresponse from visible to near infrared(NIR)(400–1800 nm) with stable and repeatable photoswitch characteristics,and the photoresponsivity reached 1.8 mA/W at 1550 nm.In addition,the polarization sensitive detection in the visible to NIR spectrum(532–1750 nm) was demonstrated,and the photodetector showed a highly polarization sensitive photocurrent with an anisotropy ratio as high as 6.44 at 1064 nm.Our study shows that van der Waals heterojunction is an effective way to realize the broadband polarization sensitive photodetection,which is of great significance to the realization and application of multi-functional devices based on 2D vdWs heterostructures.展开更多
A magnetic tunnel junction(MTJ)is the core component in memory technologies,such as the magnetic random-access memory,magnetic sensors and programmable logic devices.In particular,MTJs based on twodimensional van der ...A magnetic tunnel junction(MTJ)is the core component in memory technologies,such as the magnetic random-access memory,magnetic sensors and programmable logic devices.In particular,MTJs based on twodimensional van der Waals(vd W)heterostructures offer unprecedented opportunities for low power consumption and miniaturization of spintronic devices.However,their operation at room temperature remains a challenge.Here,we report a large tunnel magnetoresistance(TMR)of up to 85%at room temperature(T=300 K)in vdW MTJs based on a thin(<10 nm)semiconductor spacer WSe_(2)layer embedded between two Fe_(3)GaTe_(2e)lectrodes with intrinsic above-room-temperature ferromagnetism.The TMR in the MTJ increases with decreasing temperature up to 164%at T=10 K.The demonstration of TMR in ultra-thin MTJs at room temperature opens a realistic and promising route for next-generation spintronic applications beyond the current state of the art.展开更多
Wearable devices redefine the way people interact with machines.Despite the intensive effort in the design and fabrication of synthetic fibers to improve wearable device properties in terms of electronic and ionic con...Wearable devices redefine the way people interact with machines.Despite the intensive effort in the design and fabrication of synthetic fibers to improve wearable device properties in terms of electronic and ionic conductivity,stretchability,com-fort,and washability,challenges remain in fabricating single fiber materials that optimize all properties simultaneously.In this work,we demonstrate a highly stretchable,ionic,and electronic conductive fabric via(1)the natural nanoscale chan-nels in fibers for effective ion transportation,(2)confining the electronic conductive material with the cellulose fibers,and(3)decoupling the property degradation of the fiber from deformation using the knitted pattern.The hierarchical structure created by cotton fibers can serve as ionic conductive channels as well as a robust multiscale scaffold to host infiltrated elec-tronic conductive materials.Cotton strands with ionic and electronic conductivity can be knitted into fabrics that are highly stretchable(~300%).Moreover,high ionic and electronic conductivity are observed with 2 S/m and 5 S/m,respectively,even under a strain of 175%.With the inherent advantages of cotton fabrics such as moisture-wicking,washability,comfort,and light-weightiness for wearable applications,our approach of directly functionalized cellulose can potentially be a promising route towards highly stretchable and wearable mixed conductors.展开更多
Hypersonic boundary layer transition is of fundamental importance for the design of high-speed vehicles because of its direct relevance to drag and aerodynamic heating.As the focus of transition and turbulence researc...Hypersonic boundary layer transition is of fundamental importance for the design of high-speed vehicles because of its direct relevance to drag and aerodynamic heating.As the focus of transition and turbulence research is shifting towards higher velocities,research on compressible flows,especially hypersonic flows,is becoming increasingly attractive to researchers worldwide[1,2].展开更多
The effects of a wavy wall on a hypersonic boundary layer of a flared cone are investigated using experimental measurements and direct numerical simulations(DNSs). Non-contact optical measurements using a focused lase...The effects of a wavy wall on a hypersonic boundary layer of a flared cone are investigated using experimental measurements and direct numerical simulations(DNSs). Non-contact optical measurements using a focused laser differential interferometer(FLDI) show that a wavy wall can significantly suppress the second mode, and multiple perturbations of new frequencies are generated over the wavy surface, which agrees well with numerical results. Using Lagrangian tracking of marked particles, it is demonstrated that the wavy wall geometry can induce mean flow oscillations while exciting acoustic waves. The frequencies of the excited disturbances over a wavy wall agree with the classical Rossiter model. The superposition of a disturbance propagating downstream and an acoustic wave propagating upstream at the same frequency but with different amplitudes and propagation velocities results in a spatial distribution with a streamwise-oscillatory pattern over the wavy surface. A simple two-wave superposition model that takes into account the phase velocities and wavenumbers of the convective disturbance and acoustic wave can well describe the modal behavior of excited disturbances over a wavy wall.展开更多
A brief discussion is given in this note to clarify the transition path of the hypersonic boundary layer.The first mode plays an important role in the hypersonic boundary layer transition and should not be ignored.The...A brief discussion is given in this note to clarify the transition path of the hypersonic boundary layer.The first mode plays an important role in the hypersonic boundary layer transition and should not be ignored.The second mode may enhance the boundary layer transition,but it is not the decisive factor affecting the transition.展开更多
Background:Keloids are abnormal fibrous hyperplasias that are difficult to treat.Melatonin can be used to inhibit the development of certain fibrotic diseases but has never been used to treat keloids.We aimed to disco...Background:Keloids are abnormal fibrous hyperplasias that are difficult to treat.Melatonin can be used to inhibit the development of certain fibrotic diseases but has never been used to treat keloids.We aimed to discover the effects and mechanisms of melatonin in keloid fibroblasts(KFs).Methods:Flow cytometry,CCK-8 assays,western blotting,wound-healing assays,transwell assays,collagen gel contraction assays and immunofluorescence assays were applied to demonstrate the effects and mechanisms of melatonin in fibroblasts derived from normal skin,hypertrophic scars and keloids.The therapeutic potential of the combination of melatonin and 5-fluorouracil(5-FU)was investigated in KFs.Results:Melatonin significantly promoted cell apoptosis and inhibited cell proliferation,migration and invasion,contractile capability and collagen production in KFs.Further mechanistic studies demonstrated that melatonin could inhibit the cAMP/PKA/Erk and Smad pathways through the membrane receptor MT2 to alter the biological characteristics of KFs.Moreover,the combination of melatonin and 5-FU remarkably promoted cell apoptosis and inhibited cell migration and invasion,contractile capability and collagen production in KFs.Furthermore,5-FU suppressed the phosphorylation of Akt,mTOR,Smad3 and Erk,and melatonin in combination with 5-FU markedly suppressed the activation of the Akt,Erk and Smad pathways.Conclusions:Collectively,melatonin may inhibit the Erk and Smad pathways through the mem-brane receptor MT2 to alter the cell functions of KFs,while combination with 5-FU could exert even more inhibitory effects in KFs through simultaneous suppression of multiple signalling pathways.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1405100)the Beijing Natural Science Foundation Key Program(Grant No.Z220005)the National Natural Science Foundation of China(Grant Nos.12241405,12174384,and 12204058)。
文摘The discovery of ferromagnetic two-dimensional(2D)van der Waals(vdWs)materials provides an opportunity to explore intriguing physics and to develop innovative spin electronic devices.However,the main challenge for practical applications of vd Ws ferromagnetic crystals lies in the weak intrinsic ferromagnetism and small perpendicular magnetic anisotropy(PMA)above room temperature.Here,we report the intrinsic vd Ws ferromagnetic crystal Fe_(3)GaTe_(2),synthesized by the self-flux method,exhibiting a Curie temperature(TC)of 370 K,a high saturation magnetization of 33.47 emu/g,and a large PMA energy density of approximately 4.17×10^(5)J/m^(3).Furthermore,the magneto-optical effect is systematically investigated in Fe_(3)GaTe_(2).The doubly degenerate E_(2g)(Γ)mode reverses the helicity of incident photons,indicating the existence of pseudoangular-momentum(PAM)and chirality.Meanwhile,the non-degenerate non-chiral A_(1g)(Γ)phonon exhibits a significant magneto-Raman effect under an external out-of-plane magnetic field.These results lay the groundwork for studying phonon chirality and magneto-optical phenomena in 2D magnetic materials,providing the feasibility for further fundamental research and applications in spintronic devices.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1405100)the Beijing Natural Science Foundation Key Program(Grant No.Z190007)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB44000000 and XDB28000000)the National Natural Science Foundation of China(Grant Nos.12241405,11734004,and 12174028)。
文摘The emergent van der Waals magnetic material is a promising component for spintronic devices with novel functionalities.Here,we report a transition of negative-to-positive magnetoresistance in Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)van der Waals all-magnetic tunnel junctions with increasing the applied bias voltage.A negative magnetoresistance is observed first in Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)tunnel junctions,where the resistance with antiparallel aligned magnetization of two Fe_(3)GeTe_(2)electrodes is lower than that with parallel alignment,which is due to the opposite spin polarizations of two Fe_(3)GeTe_(2)electrodes.With the bias voltage increasing,the spin polarization of the biased Fe_(3)GeTe_(2)electrode is changed so that the spin orientations of two Fe_(3)GeTe_(2)electrodes are the same.Our experimental observations are supported by the calculated spin-dependent density of states for Fe_(3)GeTe_(2)electrodes under a finite bias.The significantly bias voltage-dependent spin transport properties in van der Waals magnetic tunnel junctions open a promising route for designing electrical controllable spintronic devices based on van der Waals magnets.
基金supported by the National Key R&D Program of China (Grant No. 2017YFA0303400 and No.2017YFB 0405700)supported by the NSFC Grant Nos. 61774144 and 11474272sponsored by Chinese Academy of Sciences, grant No. QYZDY-SSW-JSC020, XDPB12, and XDB28000000
文摘Two-dimensional(2D) atomic crystals,such as graphene,black phosphorus(BP) and transition metal dichalcogenides(TMDCs) are attractive for use in optoelectronic devices,due to their unique crystal structures and optical absorption properties.In this study,we fabricated BP/ReS2 van der Waals(vdWs) heterojunction devices.The devices realized broadband photoresponse from visible to near infrared(NIR)(400–1800 nm) with stable and repeatable photoswitch characteristics,and the photoresponsivity reached 1.8 mA/W at 1550 nm.In addition,the polarization sensitive detection in the visible to NIR spectrum(532–1750 nm) was demonstrated,and the photodetector showed a highly polarization sensitive photocurrent with an anisotropy ratio as high as 6.44 at 1064 nm.Our study shows that van der Waals heterojunction is an effective way to realize the broadband polarization sensitive photodetection,which is of great significance to the realization and application of multi-functional devices based on 2D vdWs heterostructures.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1405100 and 2022YFE0134600)the Beijing Natural Science Foundation Key Program(Grant No.Z190007)+2 种基金the National Natural Science Foundation of China(Grant Nos.61774144,62005265,and 52272152)the Key Research Program of Frontier Sciences(Grant No.QYZDY-SSW-JSC020)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB44000000 and XDB28000000)。
文摘A magnetic tunnel junction(MTJ)is the core component in memory technologies,such as the magnetic random-access memory,magnetic sensors and programmable logic devices.In particular,MTJs based on twodimensional van der Waals(vd W)heterostructures offer unprecedented opportunities for low power consumption and miniaturization of spintronic devices.However,their operation at room temperature remains a challenge.Here,we report a large tunnel magnetoresistance(TMR)of up to 85%at room temperature(T=300 K)in vdW MTJs based on a thin(<10 nm)semiconductor spacer WSe_(2)layer embedded between two Fe_(3)GaTe_(2e)lectrodes with intrinsic above-room-temperature ferromagnetism.The TMR in the MTJ increases with decreasing temperature up to 164%at T=10 K.The demonstration of TMR in ultra-thin MTJs at room temperature opens a realistic and promising route for next-generation spintronic applications beyond the current state of the art.
基金supported by the Research Grants Council(RGC)of the Government of Hong Kong Special Administrative Region(HKSAR)with RGC/ECS Project(Grant No.26200222)RGC/GRF Project(Grant No.16201023)+3 种基金RGC/STG Project(Grant No.STG2/E-605/23-N)Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515011779)Guangdong Province Science and Technology Plan Project(Grant No.2023A0505030005)Center for Ocean Research in Hong Kong and Macao,a joint research center between Laoshan Laboratory and HKUST,and the Project of Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone(Grant No.HZQBKCZYB-2020083).
文摘Wearable devices redefine the way people interact with machines.Despite the intensive effort in the design and fabrication of synthetic fibers to improve wearable device properties in terms of electronic and ionic conductivity,stretchability,com-fort,and washability,challenges remain in fabricating single fiber materials that optimize all properties simultaneously.In this work,we demonstrate a highly stretchable,ionic,and electronic conductive fabric via(1)the natural nanoscale chan-nels in fibers for effective ion transportation,(2)confining the electronic conductive material with the cellulose fibers,and(3)decoupling the property degradation of the fiber from deformation using the knitted pattern.The hierarchical structure created by cotton fibers can serve as ionic conductive channels as well as a robust multiscale scaffold to host infiltrated elec-tronic conductive materials.Cotton strands with ionic and electronic conductivity can be knitted into fabrics that are highly stretchable(~300%).Moreover,high ionic and electronic conductivity are observed with 2 S/m and 5 S/m,respectively,even under a strain of 175%.With the inherent advantages of cotton fabrics such as moisture-wicking,washability,comfort,and light-weightiness for wearable applications,our approach of directly functionalized cellulose can potentially be a promising route towards highly stretchable and wearable mixed conductors.
基金supported by the National Key R&D Program of China (2017YFA0303400 and 2017YFB0405700)the National Natural Science foundation of China (61774144)+2 种基金Beijing Natural Science Foundation Key Program (Z190007)the Project from Chinese Academy of Sciences (QYZDY-SSW-JSC020, XDPB12, and XDB28000000)K C Wong Education Foundation。
基金supported by the National Natural Science Foundation of China(10921202,11221061,11632002,11521091,11602005,and 91752202)the National Key Project(GJXM92579)。
文摘Hypersonic boundary layer transition is of fundamental importance for the design of high-speed vehicles because of its direct relevance to drag and aerodynamic heating.As the focus of transition and turbulence research is shifting towards higher velocities,research on compressible flows,especially hypersonic flows,is becoming increasingly attractive to researchers worldwide[1,2].
基金supported by the National Natural Science Foundation of China(Grant Nos.10921202,11221061,11632002,11521091,1160200591752202)the National Key Project(Grant No.GJXM92579)。
文摘The effects of a wavy wall on a hypersonic boundary layer of a flared cone are investigated using experimental measurements and direct numerical simulations(DNSs). Non-contact optical measurements using a focused laser differential interferometer(FLDI) show that a wavy wall can significantly suppress the second mode, and multiple perturbations of new frequencies are generated over the wavy surface, which agrees well with numerical results. Using Lagrangian tracking of marked particles, it is demonstrated that the wavy wall geometry can induce mean flow oscillations while exciting acoustic waves. The frequencies of the excited disturbances over a wavy wall agree with the classical Rossiter model. The superposition of a disturbance propagating downstream and an acoustic wave propagating upstream at the same frequency but with different amplitudes and propagation velocities results in a spatial distribution with a streamwise-oscillatory pattern over the wavy surface. A simple two-wave superposition model that takes into account the phase velocities and wavenumbers of the convective disturbance and acoustic wave can well describe the modal behavior of excited disturbances over a wavy wall.
基金National Natural Science Foundation of China(grant nos.109103010062,10921202,11372009,11602005 and 11632002)National Key Project GJXM92579.
文摘A brief discussion is given in this note to clarify the transition path of the hypersonic boundary layer.The first mode plays an important role in the hypersonic boundary layer transition and should not be ignored.The second mode may enhance the boundary layer transition,but it is not the decisive factor affecting the transition.
基金supported by the National Natural Science Foundation of China(81871565,82072180,82072181,82172213).
文摘Background:Keloids are abnormal fibrous hyperplasias that are difficult to treat.Melatonin can be used to inhibit the development of certain fibrotic diseases but has never been used to treat keloids.We aimed to discover the effects and mechanisms of melatonin in keloid fibroblasts(KFs).Methods:Flow cytometry,CCK-8 assays,western blotting,wound-healing assays,transwell assays,collagen gel contraction assays and immunofluorescence assays were applied to demonstrate the effects and mechanisms of melatonin in fibroblasts derived from normal skin,hypertrophic scars and keloids.The therapeutic potential of the combination of melatonin and 5-fluorouracil(5-FU)was investigated in KFs.Results:Melatonin significantly promoted cell apoptosis and inhibited cell proliferation,migration and invasion,contractile capability and collagen production in KFs.Further mechanistic studies demonstrated that melatonin could inhibit the cAMP/PKA/Erk and Smad pathways through the membrane receptor MT2 to alter the biological characteristics of KFs.Moreover,the combination of melatonin and 5-FU remarkably promoted cell apoptosis and inhibited cell migration and invasion,contractile capability and collagen production in KFs.Furthermore,5-FU suppressed the phosphorylation of Akt,mTOR,Smad3 and Erk,and melatonin in combination with 5-FU markedly suppressed the activation of the Akt,Erk and Smad pathways.Conclusions:Collectively,melatonin may inhibit the Erk and Smad pathways through the mem-brane receptor MT2 to alter the cell functions of KFs,while combination with 5-FU could exert even more inhibitory effects in KFs through simultaneous suppression of multiple signalling pathways.