Photoinduced intermolecular charge transfer(PICT)determines the voltage loss in bulk heterojunction(BHJ)organic photovoltaics(OPVs),and this voltage loss can be minimized by inducing efficient PICT,which requires ener...Photoinduced intermolecular charge transfer(PICT)determines the voltage loss in bulk heterojunction(BHJ)organic photovoltaics(OPVs),and this voltage loss can be minimized by inducing efficient PICT,which requires energy-state matching between the donor and acceptor at the BHJ interfaces.Thus,both geometrically and energetically accessible delocalized state matching at the hot energy level is crucial for achieving efficient PICT.In this study,an effective method for quantifying the hot state matching of OPVs was developed.The degree of energy-state matching between the electron donor and acceptor at BHJ interfaces was quantified using a mismatching factor(MF)calculated from the modified optical density of the BHJ.Furthermore,the correlation between the open-circuit voltage(Voc)of the OPV device and energy-state matching at the BHJ interface was investigated using the calculated MF.The OPVs with small absolute MF values exhibited high Voc values.This result clearly indicates that the energy-state matching between the donor and acceptor is crucial for achieving a high Voc in OPVs.Because the MF indicates the degree of energy-state matching,which is a critical factor for suppressing energy loss,it can be used to estimate the Voc loss in OPVs.展开更多
Recently, giant intrinsic anomalous Hall effect(AHE) has been observed in the materials with kagome lattice.Here, we systematically investigate the influence of high pressure on the AHE in the ferromagnet LiMn_(6)Sn_(...Recently, giant intrinsic anomalous Hall effect(AHE) has been observed in the materials with kagome lattice.Here, we systematically investigate the influence of high pressure on the AHE in the ferromagnet LiMn_(6)Sn_(6) with clean Mn kagome lattice. Our in situ high-pressure Raman spectroscopy indicates that the crystal structure of LiMn_(6)Sn_(6) maintains a hexagonal phase under high pressures up to 8.51 GPa. The anomalous Hall conductivity(AHC) σ_(xy)^(A) remains around 150 Ω^(-1)·cm^(-1), dominated by the intrinsic mechanism. Combined with theoretical calculations, our results indicate that the stable AHE under pressure in Li Mn_(6)Sn_(6) originates from the robust electronic and magnetic structure.展开更多
We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft ...We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model.We find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped electrons.The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures.We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.展开更多
Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We sy...Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We systematically investigate both the structural and electronic responses of MnBi2 Te4 and MnBi4 Te7 to external pressure.In addition to the suppression of antiferromagnetic order,MnBi2 Te4 is found to undergo a metalsemiconductor-metal transition upon compression.The resistivity of MnBi4 Te7 changes dramatically under high pressure and a non-monotonic evolution of p(T)is observed.The nontrivial topology is proved to persist before the structural phase transition observed in the high-pressure regime.We find that the bulk and surface states respond differently to pressure,which is consistent with the non-monotonic change of the resistivity.Interestingly,a pressure-induced amorphous state is observed in MnBi2 Te4,while two high-pressure phase transitions are revealed in MnBi4 Te7.Our combined theoretical and experimental research establishes MnBi2 Te4 and MnBi4 Te7 as highly tunable magnetic topological insulators,in which phase transitions and new ground states emerge upon compression.展开更多
Single-photon emitters (SPEs) are one of the key components in quantum information applications. The ideal SPEs emit a single photon or a photon-pair on demand, with high purity and distinguishability. SPEs can also b...Single-photon emitters (SPEs) are one of the key components in quantum information applications. The ideal SPEs emit a single photon or a photon-pair on demand, with high purity and distinguishability. SPEs can also be integrated in photonic circuits for scalable quantum communication and quantum computer systems. Quantum dots made from Ⅲ-Ⅴ compounds such as InGaAs or GaN have been found to be particularly attractive SPE sources due to their well studied optical performance and state of the art industrial flexibility in fabrication and integration. Here, we review the optical and optoelectronic properties and growth methods of general SPEs. Subsequently, a brief summary of the latest advantages in Ⅲ-Ⅴ compound SPEs and the research progress achieved in the past few years will be discussed. We finally describe frontier challenges and conclude with the latest SPE fabrication science and technology that can open new possibilities for quantum information applications.展开更多
Hg Te(111) surface is comprehensively studied by scanning tunneling microscopy/spectroscopy(STS).In addition to th√e prim√itive(1 × 1)√ hexagonal lattice,six reconstructed surface structures are observe...Hg Te(111) surface is comprehensively studied by scanning tunneling microscopy/spectroscopy(STS).In addition to th√e prim√itive(1 × 1)√ hexagonal lattice,six reconstructed surface structures are observed:(2 × 2),2 × 1,4 × 1,3 ×(1/2)3,2(1/2)2 × 2 and (1/2)11 × 2.The(2 × 2) reconstructed lattice maintains the primitive hexagonal symmetry,whi√le the lattices of the other five reconstructions are rectangular.Moreover,the topographic features of the3 ×(1/2)3 reconstruction are bias dependent,indicating that they have both topographic and electronic origins.The STSs obtained at different reconstructed surfaces show a universal dip feature with size ~100 mV,which may be attributed to the surface distortion.Our results reveal the atomic structure and complex reconstructions of the cleaved Hg Te(111) surfaces,which paves the way to understand the rich properties of Hg Te crystal.展开更多
As a new type of quantum state of matter hosting low energy relativistic quasiparticles,Weyl semimetals(WSMs)have attracted significant attention for scientific community and potential quantum device applications.In t...As a new type of quantum state of matter hosting low energy relativistic quasiparticles,Weyl semimetals(WSMs)have attracted significant attention for scientific community and potential quantum device applications.In this study,we present a comprehensive investigation of the structural,magnetic,and transport properties of noncentrosymmetric RAl Si(R=Sm,Ce),which have been predicted to be new magnetic WSM candidates.Both samples exhibit nonsaturated magnetoresistance,with about 900%and 80%for Sm Al Si and Ce Al Si,respectively,at temperature of 1.8 K and magnetic field of 9 T.The carrier densities of Sm Al Si and Ce Al Si exhibit remarkable change around magnetic transition temperatures,signifying that the electronic states are sensitive to the magnetic ordering of rare-earth elements.At low temperatures,Sm Al Si reveals prominent Shubnikov–de Haas oscillations associated with the nontrivial Berry phase.High-pressure experiments demonstrate that the magnetic order is robust and survival under high pressure.Our results would yield valuable insights into WSM physics and potentials in applications to next-generation spintronic devices in the RAl Si(R=Sm,Ce)family.展开更多
Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electr...Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu_(2)TlX_(2)(X = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu_(2)TlSe_(2) to a semimetal in Cu_(2)TlTe_(2), suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.展开更多
The interaction between a molecular cloud and an external agent(e.g.,a supernova remnant,plasma jet,radiation,or another cloud)is a common phenomenon throughout the Universe and can significantly change the star forma...The interaction between a molecular cloud and an external agent(e.g.,a supernova remnant,plasma jet,radiation,or another cloud)is a common phenomenon throughout the Universe and can significantly change the star formation rate within a galaxy.This process leads to fragmentation of the cloud and to its subsequent compression and can,eventually,initiate the gravitational collapse of a stable molecular cloud.It is,however,difficult to study such systems in detail using conventional techniques(numerical simulations and astronomical observations),since complex interactions of flows occur.In this paper,we experimentally investigate the compression of a foam ball by Taylor–Sedov blast waves,as an analog of supernova remnants interacting with a molecular cloud.The formation of a compression wave is observed in the foam ball,indicating the importance of such experiments for understanding how star formation is triggered by external agents.展开更多
Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on th...Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on the formation mechanism,crystallography,and photoelectric properties of the lowdimensional phase still requires further detailed study.In this work,we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts,clarifying the effect of anions on the formation of quasi-2D/3D heterojunctions.To demonstrate the importance of halide influences,we employ novel neo-pentylammonium halide salts with different halide anions(neoPAX,X=I,Br,or Cl).We find that regardless of halide selection,iodide-based(neoPA)_(2)(FA)_((n-1))PbnI_((3n+1))phases are formed above the perovskite substrate,while the added halide anions diffuse and passivate the perovskite bulk.In addition,we also find the halide choice has an influence on the degree of dimensionality(n).Comparing the three halides,we find that chloride-based salts exhibit superior crystallographic,enhanced carrier transport,and extraction compared to the iodide and bromide analogs.As a result,we report high power conversion efficiency in quasi-2D/3D PSCs,which are optimal when using chloride salts,reaching up to 23.35%,and improving long-term stability.展开更多
We give a simple introduction to the theoretical treatment of atoms interacting strongly w ith electromagnetic fields in the radiofrequency,microw ave and laser domains. In particular,w e discuss the concept of dresse...We give a simple introduction to the theoretical treatment of atoms interacting strongly w ith electromagnetic fields in the radiofrequency,microw ave and laser domains. In particular,w e discuss the concept of dressed atoms,w hich considers the combination of the atom and photons as a composite physical system. This pow erful concept has a w ide range of applications in atomic physics and w e give a few examples of its use in the manipulation of ultracold atoms in adiabatic potentials. These examples are selected from experimental w ork conducted by our research team in Oxford but there are numerous other applications and w e outline some future possibilities.展开更多
Angle-resolved photoemission spectroscopy(ARPES)and torque magnetometry(TM)measurements have been carried out to study the electronic structures of a correlated topological insulator(TI)candidate Yb B6.We observed cle...Angle-resolved photoemission spectroscopy(ARPES)and torque magnetometry(TM)measurements have been carried out to study the electronic structures of a correlated topological insulator(TI)candidate Yb B6.We observed clear surface states on the[001]surface centered at theГ^- and М^- points of the surface Brillouin zone.Interestingly,the fermiology revealed by the quantum oscillation of TM measurements agrees excellently with ARPES measurements.Moreover,the band structures we observed suggest that the band inversion in Yb B6 happens between the Yb5 dand B2bands,instead of the Yb5dand Yb4fbands as suggested by previous theoretical investigation,which will help settle the heavy debate regarding the topological nature of samarium/ytterbium hexaborides.展开更多
Photonic quantum computation plays an important role and offers unique advantages.Two decades after the milestone work of Knill-Laflamme-Milburn,various architectures of photonic processors have been proposed,and quan...Photonic quantum computation plays an important role and offers unique advantages.Two decades after the milestone work of Knill-Laflamme-Milburn,various architectures of photonic processors have been proposed,and quantum advantage over classical computers has also been demonstrated.It is now the opportune time to apply this technology to real-world applications.However,at current technology level,this aim is restricted by either programmability in bulk optics or loss in integrated optics for the existing architectures of processors,for which the resource cost is also a problem.Here we present a von-Neumann-like architecture based on temporal-mode encoding and looped structure on table,which is capable of multimode-universal programmability,resource-efficiency,phasestability and software-scalability.In order to illustrate these merits,we execute two different programs with varying resource requirements on the same processor,to investigate quantum signature of chaos from two aspects:the signature behaviors exhibited in phase space(13 modes),and the Fermi golden rule which has not been experimentally studied in quantitative way before(26 modes).The maximal program contains an optical interferometer network with 1694 freely-adjustable phases.Considering current state-of-the-art,our architecture stands as the most promising candidate for real-world applications.展开更多
Presented is a novel way to combine snapshot compressive imaging and lateral shearing interferometry in order to capture the spatio-spectral phase of an ultrashort laser pulse in a single shot.A deep unrolling algorit...Presented is a novel way to combine snapshot compressive imaging and lateral shearing interferometry in order to capture the spatio-spectral phase of an ultrashort laser pulse in a single shot.A deep unrolling algorithm is utilized for snapshot compressive imaging reconstruction due to its parameter efficiency and superior speed relative to other methods,potentially allowing for online reconstruction.The algorithm’s regularization term is represented using a neural network with 3D convolutional layers to exploit the spatio-spectral correlations that exist in laser wavefronts.Compressed sensing is not typically applied to modulated signals,but we demonstrate its success here.Furthermore,we train a neural network to predict the wavefronts from a lateral shearing interferogram in terms of Zernike polynomials,which again increases the speed of our technique without sacrificing fidelity.This method is supported with simulation-based results.While applied to the example of lateral shearing interferometry,the methods presented here are generally applicable to a wide range of signals,including Shack-Hartmann-type sensors.The results may be of interest beyond the context of laser wavefront characterization,including within quantitative phase imaging.展开更多
Laser-plasma physics has developed rapidly over the past few decades as lasers have become both more powerful and more widely available.Early experimental and numerical research in this field was dominated by single-s...Laser-plasma physics has developed rapidly over the past few decades as lasers have become both more powerful and more widely available.Early experimental and numerical research in this field was dominated by single-shot experiments with limited parameter exploration.However,recent technological improvements make it possible to gather data for hundreds or thousands of different settings in both experiments and simulations.This has sparked interest in using advanced techniques from mathematics,statistics and computer science to deal with,and benefit from,big data.At the same time,sophisticated modeling techniques also provide new ways for researchers to deal effectively with situation where still only sparse data are available.This paper aims to present an overview of relevant machine learning methods with focus on applicability to laser-plasma physics and its important sub-fields of laser-plasma acceleration and inertial confinement fusion.展开更多
Optical gain enhancement of two-dimensional CsPbBr3 nanosheets was studied when the amplified spontaneous emission is guided by a patterned structure of polyurethane-acrylate.Given the uncertainties and pitfalls in re...Optical gain enhancement of two-dimensional CsPbBr3 nanosheets was studied when the amplified spontaneous emission is guided by a patterned structure of polyurethane-acrylate.Given the uncertainties and pitfalls in retrieving a gain coefficient from the variable stripe length method,a gain contour g((h))ω.x)was obtained in the plane of spectrum energy(hω)and stripe length(x),whereby an average gain was obtained,and gain saturation was analysed.Excitation and temperature dependence of the gain contour show that the waveguide enhances both gain and thermal stability due to the increased optical confinement and heat dissipation,and the gain origins were attributed to the two-dimensional excitons and the localized states.展开更多
Quantum computing has shown great potential in various quantum chemical applications such as drug discovery,material design,and catalyst optimization.Although significant progress has been made in the quantum simulati...Quantum computing has shown great potential in various quantum chemical applications such as drug discovery,material design,and catalyst optimization.Although significant progress has been made in the quantum simulation of simple molecules,ab initio simulation of solid-state materials on quantum computers is still in its early stage,mostly owing to the fact that the system size quickly becomes prohibitively large when approaching the thermodynamic limit.In this work,we introduce an orbital-based multifragment approach on top of the periodic density matrix embedding theory,resulting in a significantly smaller problem size for the current near-term quantum computer.We demonstrate the accuracy and efficiency of our method compared with the conventional methodologies and experiments on solid-state systems with complex electronic structures.These include spin-polarized states of a hydrogen chain(1D-H),the equation of state of a boron nitride layer(h-BN)as well as the magnetic ordering in nickel oxide(NiO),a prototypical strongly correlated solid.Our results suggest that quantum embedding combined with a chemically intuitive fragmentation can greatly advance quantum simulation of realistic materials,thereby paving the way for solving important yet classically hard industrial problems on near-term quantum devices.展开更多
Diminishing surface defect states in perovskite nancx^rystals is a highly challenging subject for enhancing optoelectronic device performance.We synthesized organic/inorganic lead-halide perovskite MAPbBr3(MA=methylam...Diminishing surface defect states in perovskite nancx^rystals is a highly challenging subject for enhancing optoelectronic device performance.We synthesized organic/inorganic lead-halide perovskite MAPbBr3(MA=methylammonium)clusters comprising nanocrystals with diameters ranging between 20 and 30 nm and characterized an enhanced photoluminescence(PL)quantum yield(as much as^7 times)by encapsulating the MAPbBr3 with graphene(Gr).The optical properties of MAPbBr3 and Gr/MAPbBr3 were investigated by temperature-dependent micro-PL and time-resolved PL measurements.Density functional theory calculations show that the surface defect states in MAPbBr3 are removed and the optical band gap is reduced by a 0.15 eV by encapsulation with graphene due to partial restoration of lattice distortions.展开更多
Since 2005, there has been a huge growth in the use of engineered control pulses to perform desired quantum operations in systems such as nuclear magnetic resonance quantum information processors. These approaches, wh...Since 2005, there has been a huge growth in the use of engineered control pulses to perform desired quantum operations in systems such as nuclear magnetic resonance quantum information processors. These approaches, which build on the original gradient ascent pulse engineering algorithm, remain computationally intensive because of the need to calculate matrix exponentials for each time step in the control pulse. In this study, we discuss how the propagators for each time step can be approximated using the Trotter-Suzuki formula, and a further speedup achieved by avoiding unnecessary operations. The resulting procedure can provide substantial speed gain with negligible costs in the propagator error, providing a more practical approach to pulse en-ineerinK.展开更多
基金National Research Foundation of Korea,Grant/Award Number:2022R1A6A1A03051158BrainLink Program,Grant/Award Number:2022H1D3A3A01077343Nano Material Technology Development Program,Grant/Award Number:2021M3H4A1A02057007。
文摘Photoinduced intermolecular charge transfer(PICT)determines the voltage loss in bulk heterojunction(BHJ)organic photovoltaics(OPVs),and this voltage loss can be minimized by inducing efficient PICT,which requires energy-state matching between the donor and acceptor at the BHJ interfaces.Thus,both geometrically and energetically accessible delocalized state matching at the hot energy level is crucial for achieving efficient PICT.In this study,an effective method for quantifying the hot state matching of OPVs was developed.The degree of energy-state matching between the electron donor and acceptor at BHJ interfaces was quantified using a mismatching factor(MF)calculated from the modified optical density of the BHJ.Furthermore,the correlation between the open-circuit voltage(Voc)of the OPV device and energy-state matching at the BHJ interface was investigated using the calculated MF.The OPVs with small absolute MF values exhibited high Voc values.This result clearly indicates that the energy-state matching between the donor and acceptor is crucial for achieving a high Voc in OPVs.Because the MF indicates the degree of energy-state matching,which is a critical factor for suppressing energy loss,it can be used to estimate the Voc loss in OPVs.
基金supported by the National Natural Science Foundation of China (Grant No. 52272265)the National Key R&D Program of China (Grant Nos. 2023YFA1607400 and 2018YFA0704300)+4 种基金the support from the National Natural Science Foundation of China (Grant Nos. 52271016 and 52188101)the support from Analytical Instrumentation Center (# SPST-AIC10112914), SPST, Shanghai Tech Universitythe European Research Council (ERC Advanced Grant No. 742068 ‘TOPMAT’)the DFG through SFB 1143 (Project ID 247310070)the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat (EXC2147,Project ID 390858490)。
文摘Recently, giant intrinsic anomalous Hall effect(AHE) has been observed in the materials with kagome lattice.Here, we systematically investigate the influence of high pressure on the AHE in the ferromagnet LiMn_(6)Sn_(6) with clean Mn kagome lattice. Our in situ high-pressure Raman spectroscopy indicates that the crystal structure of LiMn_(6)Sn_(6) maintains a hexagonal phase under high pressures up to 8.51 GPa. The anomalous Hall conductivity(AHC) σ_(xy)^(A) remains around 150 Ω^(-1)·cm^(-1), dominated by the intrinsic mechanism. Combined with theoretical calculations, our results indicate that the stable AHE under pressure in Li Mn_(6)Sn_(6) originates from the robust electronic and magnetic structure.
文摘We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model.We find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped electrons.The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures.We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.
基金Supported by the National Key Research and Development Program of China under Grant Nos.2018YFA0704300 and2017YFE0131300the National Natural Science Foundation of China under Grant Nos.U1932217,11974246,11874263 and10225417+1 种基金the Natural Science Foundation of Shanghai under Grant No.19ZR1477300the support from Analytical Instrumentation Center(SPST-AIC10112914),SPST,ShanghaiTech Universitysupported by Collaborative Research Project of Materials and Structures Laboratory,Tokyo Institute of Technology,Japan,Part of this research is supported by COMPRES(NSF Cooperative Agreement EAR-1661511)。
文摘Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We systematically investigate both the structural and electronic responses of MnBi2 Te4 and MnBi4 Te7 to external pressure.In addition to the suppression of antiferromagnetic order,MnBi2 Te4 is found to undergo a metalsemiconductor-metal transition upon compression.The resistivity of MnBi4 Te7 changes dramatically under high pressure and a non-monotonic evolution of p(T)is observed.The nontrivial topology is proved to persist before the structural phase transition observed in the high-pressure regime.We find that the bulk and surface states respond differently to pressure,which is consistent with the non-monotonic change of the resistivity.Interestingly,a pressure-induced amorphous state is observed in MnBi2 Te4,while two high-pressure phase transitions are revealed in MnBi4 Te7.Our combined theoretical and experimental research establishes MnBi2 Te4 and MnBi4 Te7 as highly tunable magnetic topological insulators,in which phase transitions and new ground states emerge upon compression.
文摘Single-photon emitters (SPEs) are one of the key components in quantum information applications. The ideal SPEs emit a single photon or a photon-pair on demand, with high purity and distinguishability. SPEs can also be integrated in photonic circuits for scalable quantum communication and quantum computer systems. Quantum dots made from Ⅲ-Ⅴ compounds such as InGaAs or GaN have been found to be particularly attractive SPE sources due to their well studied optical performance and state of the art industrial flexibility in fabrication and integration. Here, we review the optical and optoelectronic properties and growth methods of general SPEs. Subsequently, a brief summary of the latest advantages in Ⅲ-Ⅴ compound SPEs and the research progress achieved in the past few years will be discussed. We finally describe frontier challenges and conclude with the latest SPE fabrication science and technology that can open new possibilities for quantum information applications.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301003 and 2016YFA0300403the National Natural Science Foundation of China under Grant Nos 11521404,11634009,U1632102,11504230,11674222,11574202,11674226,11574201 and U1632272
文摘Hg Te(111) surface is comprehensively studied by scanning tunneling microscopy/spectroscopy(STS).In addition to th√e prim√itive(1 × 1)√ hexagonal lattice,six reconstructed surface structures are observed:(2 × 2),2 × 1,4 × 1,3 ×(1/2)3,2(1/2)2 × 2 and (1/2)11 × 2.The(2 × 2) reconstructed lattice maintains the primitive hexagonal symmetry,whi√le the lattices of the other five reconstructions are rectangular.Moreover,the topographic features of the3 ×(1/2)3 reconstruction are bias dependent,indicating that they have both topographic and electronic origins.The STSs obtained at different reconstructed surfaces show a universal dip feature with size ~100 mV,which may be attributed to the surface distortion.Our results reveal the atomic structure and complex reconstructions of the cleaved Hg Te(111) surfaces,which paves the way to understand the rich properties of Hg Te crystal.
基金supported by the National Key R&D Program of China(Grant Nos.2018YFA0704300 and 2017YFB0503302)the National Natural Science Foundation of China(Grant Nos.U1932217,11974246,12004252,61771234,and 12004251)+6 种基金the Natural Science Foundation of Shanghai(Grant Nos.19ZR1477300 and 20ZR1436100)the Science and Technology Commission of Shanghai Municipality(Grant Nos.19JC1413900 and YDZX20203100001438)the Shanghai Science and Technology Plan(Grant No.21DZ2260400),the Shanghai Sailing Program(Grant No.21YF1429200)the Interdisciplinary Program of Wuhan National High Magnetic Field Center(Grant No.WHMFC202124)the Beijing National Laboratory for Condensed Matter Physicsthe support from Analytical Instrumentation Center(Grant No.SPST-AIC10112914)Centre for High-resolution Electron Microscopy(ChEM)(Grant No.EM02161943),SPST,Shanghai Tech University。
文摘As a new type of quantum state of matter hosting low energy relativistic quasiparticles,Weyl semimetals(WSMs)have attracted significant attention for scientific community and potential quantum device applications.In this study,we present a comprehensive investigation of the structural,magnetic,and transport properties of noncentrosymmetric RAl Si(R=Sm,Ce),which have been predicted to be new magnetic WSM candidates.Both samples exhibit nonsaturated magnetoresistance,with about 900%and 80%for Sm Al Si and Ce Al Si,respectively,at temperature of 1.8 K and magnetic field of 9 T.The carrier densities of Sm Al Si and Ce Al Si exhibit remarkable change around magnetic transition temperatures,signifying that the electronic states are sensitive to the magnetic ordering of rare-earth elements.At low temperatures,Sm Al Si reveals prominent Shubnikov–de Haas oscillations associated with the nontrivial Berry phase.High-pressure experiments demonstrate that the magnetic order is robust and survival under high pressure.Our results would yield valuable insights into WSM physics and potentials in applications to next-generation spintronic devices in the RAl Si(R=Sm,Ce)family.
基金supported by the National Natural Science Foundation of China (Grant No. 11774190)。
文摘Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu_(2)TlX_(2)(X = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu_(2)TlSe_(2) to a semimetal in Cu_(2)TlTe_(2), suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.
基金the support of Investissements d’Avenir of LabEx PALM(Grant No.ANR-10-LABX-0039-PALM)the Ministry of Science and Higher Education of the Russian Federation(Agreement with Joint Institute for High Temperatures RAS No.075-15-2020-785)G.G.acknowledges support from the UK EPSRC(Grant Nos.EP/M022331/1 and EP/N014472/1)。
文摘The interaction between a molecular cloud and an external agent(e.g.,a supernova remnant,plasma jet,radiation,or another cloud)is a common phenomenon throughout the Universe and can significantly change the star formation rate within a galaxy.This process leads to fragmentation of the cloud and to its subsequent compression and can,eventually,initiate the gravitational collapse of a stable molecular cloud.It is,however,difficult to study such systems in detail using conventional techniques(numerical simulations and astronomical observations),since complex interactions of flows occur.In this paper,we experimentally investigate the compression of a foam ball by Taylor–Sedov blast waves,as an analog of supernova remnants interacting with a molecular cloud.The formation of a compression wave is observed in the foam ball,indicating the importance of such experiments for understanding how star formation is triggered by external agents.
基金X.L.and T.W.are contributed equally to this work.W.Z.acknowledges the Engineering and Physical Sciences Research Council(EPSRC)New Investigator Award(2018EP/R043272/1)+8 种基金Marie Skłodowska-Curie Actions Individual Fellowships(839136)H.L.acknowledges the Newton Advanced Fellowship(192097)X.L.acknowledges the financial support from Zhengzhou University ScholarshipT.W thanks the University of Surrey Doctoral College for financial supportS.J.S.gratefully acknowledges the support of EPSRC(UK)under grant number EP/N021037/1L.D.thanks the China Scholarship Council and the Cambridge Trusts for fundingR.C.K.and J.A.S.thank the company Xenocs for their ongoing support through the X-ray scattering user program at the University of Sheffield and the EPSRC for funding the purchase of this instrumentZ.W.,Y.S.,and G.S.thank the financial support from Zhengzhou Materials Genome InstituteS.D.S.and K.J.acknowledge the Royal Society for funding。
文摘Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on the formation mechanism,crystallography,and photoelectric properties of the lowdimensional phase still requires further detailed study.In this work,we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts,clarifying the effect of anions on the formation of quasi-2D/3D heterojunctions.To demonstrate the importance of halide influences,we employ novel neo-pentylammonium halide salts with different halide anions(neoPAX,X=I,Br,or Cl).We find that regardless of halide selection,iodide-based(neoPA)_(2)(FA)_((n-1))PbnI_((3n+1))phases are formed above the perovskite substrate,while the added halide anions diffuse and passivate the perovskite bulk.In addition,we also find the halide choice has an influence on the degree of dimensionality(n).Comparing the three halides,we find that chloride-based salts exhibit superior crystallographic,enhanced carrier transport,and extraction compared to the iodide and bromide analogs.As a result,we report high power conversion efficiency in quasi-2D/3D PSCs,which are optimal when using chloride salts,reaching up to 23.35%,and improving long-term stability.
基金funded by EPSRC grant EP/J008028/1 and through the EU Collaborative project Qu Pro CS(Grant Agreement 641277)support from National University of Defense Technology,China
文摘We give a simple introduction to the theoretical treatment of atoms interacting strongly w ith electromagnetic fields in the radiofrequency,microw ave and laser domains. In particular,w e discuss the concept of dressed atoms,w hich considers the combination of the atom and photons as a composite physical system. This pow erful concept has a w ide range of applications in atomic physics and w e give a few examples of its use in the manipulation of ultracold atoms in adiabatic potentials. These examples are selected from experimental w ork conducted by our research team in Oxford but there are numerous other applications and w e outline some future possibilities.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11774190, 11674229, 11634009, and 11774427)the National Key R&D Program of China (Grant Nos. 2017YFA0304600 and 2017YFA0305400)+5 种基金support from the EPSRC (UK) grant EP/K04074X/1 and a DARPA (US) MESO project (No. N66001-11-1-4105)supported by the Office of Naval Research through the National Science Foundation under Award No. DMR-1707620 (magnetization measurement)supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DE-AC0205CH11231)SIMES and SLAC National Accelerator Laboratory is supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DE-AC0276SF00515)Nanjing University is supported by the National Basic Research Program of China (Grant No. 51002074)the National Basic Research of China (Grant Nos. 2012CB921503 and 2012CB632702)
文摘Angle-resolved photoemission spectroscopy(ARPES)and torque magnetometry(TM)measurements have been carried out to study the electronic structures of a correlated topological insulator(TI)candidate Yb B6.We observed clear surface states on the[001]surface centered at theГ^- and М^- points of the surface Brillouin zone.Interestingly,the fermiology revealed by the quantum oscillation of TM measurements agrees excellently with ARPES measurements.Moreover,the band structures we observed suggest that the band inversion in Yb B6 happens between the Yb5 dand B2bands,instead of the Yb5dand Yb4fbands as suggested by previous theoretical investigation,which will help settle the heavy debate regarding the topological nature of samarium/ytterbium hexaborides.
基金the Innovation Program for Quantum Science and Technology(No.2021ZD0301200)the National Natural Science Foundation of China(Nos.11874343,11821404,12174370 and 12174376)+3 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2017492)the Open Research Projects of Zhejiang Lab(No.2021MB0AB02)China Postdoctoral Science Foundation funded projects(No.2020M681949)the Fok Ying-Tong Education Foundation(No.171007).
文摘Photonic quantum computation plays an important role and offers unique advantages.Two decades after the milestone work of Knill-Laflamme-Milburn,various architectures of photonic processors have been proposed,and quantum advantage over classical computers has also been demonstrated.It is now the opportune time to apply this technology to real-world applications.However,at current technology level,this aim is restricted by either programmability in bulk optics or loss in integrated optics for the existing architectures of processors,for which the resource cost is also a problem.Here we present a von-Neumann-like architecture based on temporal-mode encoding and looped structure on table,which is capable of multimode-universal programmability,resource-efficiency,phasestability and software-scalability.In order to illustrate these merits,we execute two different programs with varying resource requirements on the same processor,to investigate quantum signature of chaos from two aspects:the signature behaviors exhibited in phase space(13 modes),and the Fermi golden rule which has not been experimentally studied in quantitative way before(26 modes).The maximal program contains an optical interferometer network with 1694 freely-adjustable phases.Considering current state-of-the-art,our architecture stands as the most promising candidate for real-world applications.
基金supported by the Independent Junior Research Group‘Characterization and control of high-intensity laser pulses for particle acceleration’,DFG Project No.453619281We would also like to acknowledge UKRI-STFC grant ST/V001655/1.
文摘Presented is a novel way to combine snapshot compressive imaging and lateral shearing interferometry in order to capture the spatio-spectral phase of an ultrashort laser pulse in a single shot.A deep unrolling algorithm is utilized for snapshot compressive imaging reconstruction due to its parameter efficiency and superior speed relative to other methods,potentially allowing for online reconstruction.The algorithm’s regularization term is represented using a neural network with 3D convolutional layers to exploit the spatio-spectral correlations that exist in laser wavefronts.Compressed sensing is not typically applied to modulated signals,but we demonstrate its success here.Furthermore,we train a neural network to predict the wavefronts from a lateral shearing interferogram in terms of Zernike polynomials,which again increases the speed of our technique without sacrificing fidelity.This method is supported with simulation-based results.While applied to the example of lateral shearing interferometry,the methods presented here are generally applicable to a wide range of signals,including Shack-Hartmann-type sensors.The results may be of interest beyond the context of laser wavefront characterization,including within quantitative phase imaging.
基金The authors acknowledge the use of GPT-3[288](text-davinci-003)in the copy-editing process of this manuscript.
文摘Laser-plasma physics has developed rapidly over the past few decades as lasers have become both more powerful and more widely available.Early experimental and numerical research in this field was dominated by single-shot experiments with limited parameter exploration.However,recent technological improvements make it possible to gather data for hundreds or thousands of different settings in both experiments and simulations.This has sparked interest in using advanced techniques from mathematics,statistics and computer science to deal with,and benefit from,big data.At the same time,sophisticated modeling techniques also provide new ways for researchers to deal effectively with situation where still only sparse data are available.This paper aims to present an overview of relevant machine learning methods with focus on applicability to laser-plasma physics and its important sub-fields of laser-plasma acceleration and inertial confinement fusion.
基金supported by the NRF funded by the Ministry of Science,MSIT,and ICT(BrainLink RS-2023-00236798,RLRC 2022R1A5A8023404,NRF-2022R1I1A1A01064278,NRF-2021R1A5A1032937,RF-2021M3H4A6A02045432).
文摘Optical gain enhancement of two-dimensional CsPbBr3 nanosheets was studied when the amplified spontaneous emission is guided by a patterned structure of polyurethane-acrylate.Given the uncertainties and pitfalls in retrieving a gain coefficient from the variable stripe length method,a gain contour g((h))ω.x)was obtained in the plane of spectrum energy(hω)and stripe length(x),whereby an average gain was obtained,and gain saturation was analysed.Excitation and temperature dependence of the gain contour show that the waveguide enhances both gain and thermal stability due to the increased optical confinement and heat dissipation,and the gain origins were attributed to the two-dimensional excitons and the localized states.
文摘Quantum computing has shown great potential in various quantum chemical applications such as drug discovery,material design,and catalyst optimization.Although significant progress has been made in the quantum simulation of simple molecules,ab initio simulation of solid-state materials on quantum computers is still in its early stage,mostly owing to the fact that the system size quickly becomes prohibitively large when approaching the thermodynamic limit.In this work,we introduce an orbital-based multifragment approach on top of the periodic density matrix embedding theory,resulting in a significantly smaller problem size for the current near-term quantum computer.We demonstrate the accuracy and efficiency of our method compared with the conventional methodologies and experiments on solid-state systems with complex electronic structures.These include spin-polarized states of a hydrogen chain(1D-H),the equation of state of a boron nitride layer(h-BN)as well as the magnetic ordering in nickel oxide(NiO),a prototypical strongly correlated solid.Our results suggest that quantum embedding combined with a chemically intuitive fragmentation can greatly advance quantum simulation of realistic materials,thereby paving the way for solving important yet classically hard industrial problems on near-term quantum devices.
基金supported by the National Natural Science Foundation of China(12004252,52272265,U1932217,11974246,52072400,52025025,and 92065109)the National Key R&D Program of China(2018YFA0704300,2021YFA1401800,2018YFE0202601,2020YFA0308800,and 2022YFA1403400)+2 种基金Shanghai Science and Technology Plan(21DZ2260400)Beijing Natural Science Foundation(Z190010,Z210006,and Z190006)the support from the Analytical Instrumentation Center(#SPST-AIC10112914),School of Physical Science and Technology(SPST),ShanghaiTech University。
基金This work was supported by Basic Science Research Program and National H onor Scientist Program through the National Research Foundation of Korea(NRF)(Nos.2010-0020414,2015R1D1A1A01058332,2018R1D1A1B07043676,2019R1A4A1029237).K.S.K.acknowledges the support from KISTI(Nos.KSC-2018-CRE-0077,KSC-2018-CHA-0057).C.W.M.acknowledges the support from KISTI(Nos.KSC-2018-CRE-0071,KSC-2019-CRE-0139,KSC-2019-CRE-0248).
文摘Diminishing surface defect states in perovskite nancx^rystals is a highly challenging subject for enhancing optoelectronic device performance.We synthesized organic/inorganic lead-halide perovskite MAPbBr3(MA=methylammonium)clusters comprising nanocrystals with diameters ranging between 20 and 30 nm and characterized an enhanced photoluminescence(PL)quantum yield(as much as^7 times)by encapsulating the MAPbBr3 with graphene(Gr).The optical properties of MAPbBr3 and Gr/MAPbBr3 were investigated by temperature-dependent micro-PL and time-resolved PL measurements.Density functional theory calculations show that the surface defect states in MAPbBr3 are removed and the optical band gap is reduced by a 0.15 eV by encapsulation with graphene due to partial restoration of lattice distortions.
文摘Since 2005, there has been a huge growth in the use of engineered control pulses to perform desired quantum operations in systems such as nuclear magnetic resonance quantum information processors. These approaches, which build on the original gradient ascent pulse engineering algorithm, remain computationally intensive because of the need to calculate matrix exponentials for each time step in the control pulse. In this study, we discuss how the propagators for each time step can be approximated using the Trotter-Suzuki formula, and a further speedup achieved by avoiding unnecessary operations. The resulting procedure can provide substantial speed gain with negligible costs in the propagator error, providing a more practical approach to pulse en-ineerinK.