Neural network force fields have significantly advanced ab initio atomistic simulations across diverse fields.However,their application in the realm of magnetic materials is still in its early stage due to challenges ...Neural network force fields have significantly advanced ab initio atomistic simulations across diverse fields.However,their application in the realm of magnetic materials is still in its early stage due to challenges posed by the subtle magnetic energy landscape and the difficulty of obtaining training data.Here we introduce a data-efficient neural network architecture to represent density functional theory total energy,atomic forces,and magnetic forces as functions of atomic and magnetic structures.Our approach incorporates the principle of equivariance under the three-dimensional Euclidean group into the neural network model.Through systematic experiments on various systems,including monolayer magnets,curved nanotube magnets,and moiré-twisted bilayer magnets of CrI_(3),we showcase the method’s high efficiency and accuracy,as well as exceptional generalization ability.The work creates opportunities for exploring magnetic phenomena in large-scale materials systems.展开更多
Spin-orbit coupling is an important ingredient to regulate the many-body physics,especially for many spin liquid candidate materials such as rare-earth magnets and Kitaev materials.The rare-earth chalcogenides NaYbCh_...Spin-orbit coupling is an important ingredient to regulate the many-body physics,especially for many spin liquid candidate materials such as rare-earth magnets and Kitaev materials.The rare-earth chalcogenides NaYbCh_(2)(Ch=O,S,Se)is a congenital frustrating system to exhibit the intrinsic landmark of spin liquid by eliminating both the site disorders between Na+and Yb^(3+)ions with the big ionic size difference and the Dzyaloshinskii-Moriya interaction with the perfect triangular lattice of the Yb^(3+)ions.The temperature versus magnetic-field phase diagram is established by the magnetization,specific heat,and neutron-scattering measurements.Notably,the neutron diffraction spectra and the magnetization curve might provide microscopic evidence for a series of spin configuration for in-plane fields,which include the disordered spin liquid state,120°antiferromagnet,and one-half magnetization state.Furthermore,the ground state is suggested to be a gapless spin liquid from inelastic neutron scattering,and the magnetic field adjusts the spin orbit coupling.Therefore,the strong spin-orbit coupling in the frustrated quantum magnet substantially enriches low-energy spin physics.This rare-earth family could offer a good platform for exploring the quantum spin liquid ground state and quantum magnetic transitions.展开更多
The superconducting tunneling effect in heterostructures,describing the process where single electrons or Cooper pairs tunnel through the barrier,can always play a significant role in understanding the phase coherence...The superconducting tunneling effect in heterostructures,describing the process where single electrons or Cooper pairs tunnel through the barrier,can always play a significant role in understanding the phase coherence and pairing mechanisms in superconductors.Taking advantage of the easy cleavage to atomically-thin monolayer structure of layered superconductors and resulting quantum confinement of electrons or Cooper pairs at two-dimensional limit,van der Waals superconducting materials hosting superconducting order in monolayers or heterostructures can exhibit extensive emergent phenomena associated with quantum phase transitions of vortex and anti-vortex pairs.Examples of superconducting tunnel junctions(STJs)based on layered superconductors have been demonstrated to achieve novel phenomena,including Andreev bound states,Majorana bound states and 0/π-phase junctions.Since the characteristic parameters of quasiparticle tunneling through the barrier are directly associated with the energy gap values of superconductors,such critical parameter can be obtained within the STJ device geometry,which helps us understand and control the pairing states and emerging phenomena in superconductors.In this review,from the perspective of STJs with single electron tunneling and Cooper pair tunneling,we discuss Andreev reflection,Majorana bound states,photon-induced tunneling effects,non-reciprocal transport and superconducting diode phenomena,as well as prospects for layered-superconductor-based STJs.展开更多
Quantum key distribution(QKD)holds the potential to establish secure keys over long distances.The distance of point-to-point QKD secure key distribution is primarily impeded by the transmission loss inherent to the ch...Quantum key distribution(QKD)holds the potential to establish secure keys over long distances.The distance of point-to-point QKD secure key distribution is primarily impeded by the transmission loss inherent to the channel.In the quest to realize a large-scale quantum network,increasing the QKD distance under current technology is of great research interest.Here we adopt the 3-intensity sending-or-not-sending twin-field QKD(TF-QKD)protocol with the actively-odd-parity-pairing method.The experiment demonstrates the feasibility of secure QKD over a 1002 km fibre channel considering the finite size effect.The secure key rate is 3.11×10^(–12)per pulse at this distance.Furthermore,by optimizing parameters for shorter fiber distances,we conducted performance tests on key distribution for fiber lengths ranging from 202 km to 505 km.Notably,the secure key rate for the 202 km,the normal distance between major cities,reached 111.74 kbps.展开更多
The profound impact of excited magnetic states on the intricate interplay between electron and lattice behaviors in magnetic materials is a topic of great interest.Unfortunately,despite the significant strides that ha...The profound impact of excited magnetic states on the intricate interplay between electron and lattice behaviors in magnetic materials is a topic of great interest.Unfortunately,despite the significant strides that have been made in first-principles methods,accurately tracking these phenomena remains a challenging and elusive task.The crux of the challenge that lies before us is centered on the intricate task of characterizing the magnetic configuration of an excited state,utilizing a first-principle approach that is firmly rooted in the ground state of the system.We propose a versatile self-adaptive spin-constrained density functional theory formalism.By iteratively optimizing the constraining field alongside the electron wave function during energy minimization,we are able to obtain an accurate potential energy surface that captures the longitudinal and transverse variations of magnetization in itinerant ferromagnetic Fe.Moreover,this technique allows us to identify the subtle coupling between magnetic moments and other degrees of freedom by tracking energy variation,providing new insights into the intricate interplay between magnetic interactions,electronic band structure,and phonon dispersion curves in single-layered CrI_(3).This new methodology represents a significant breakthrough in our ability to probe the complex and multifaceted properties of magnetic systems.展开更多
Topological materials usually possess protected gapless states in either the boundary or bulk,exhibiting various properties such as spin-momentum locking,Klein tunneling,Fermi arcs and so on.Database searches using sy...Topological materials usually possess protected gapless states in either the boundary or bulk,exhibiting various properties such as spin-momentum locking,Klein tunneling,Fermi arcs and so on.Database searches using symmetry data at high-symmetry points have catalogued thousands of topological materials revealing a magnitude of band nodes(BNs)at high-symmetry points or lying within high-symmetry lines/planes.A complete mapping from symmetry data(namely,representation of little group)in any BN to the k·p model characterizing low-energy Hamiltonian around the BN(and from the k·p model to concrete BN,inversely),is expected to complete the characterization of all BNs and gapless states.Here we first review recent progress on classifying BNs by systematically and automatically constructing k·p models based on recently completed tabulation of all irreducible(co-)representation matrices of little groups of the 1651 magnetic space groups.As one indispensable input in constructing a symmetry-allowed and generic k·p model,the expansion order,has been carefully and systematically truncated for any BN to a reasonable nonzero integer,by comparing the emanating nodal structure(ENS,including nodal point,nodal line and nodal surface)near the BN obtained by the explicitly constructed k·p model and that by pure symmetry analysis using compatibility relations(CRs).Owing to the progress,we are able to summarize all 25 different configurations of ENS near BN required by CRs,provide a complete mapping from k·p model to its realization around BN,and the corresponding ENS by CRs in an accessible file,and also reveal the protection mechanism of additional nodal lines that escape conventional analysis by CRs and is only predictable by constructing k·p model.The symmetry-based classification results on all BNs could facilitate large-scale materials prediction and hold promise for realizing topological semimetals suitable for device applications.展开更多
Upon femtosecond laser excitation in quantum materials,it is possible to study the many-body interactions through the non-equilibrium processes,realize ultrafast electronic phase transitions,and achieve photoinduced n...Upon femtosecond laser excitation in quantum materials,it is possible to study the many-body interactions through the non-equilibrium processes,realize ultrafast electronic phase transitions,and achieve photoinduced novel states or hidden states.Such studies of the interaction between the ultrafast laser and the quantum materials are the frontiers and attract significant research interests in the field of condensed matter physics.Time-and angle-resolved photoemission spectroscopy is a key experimental tool to study the ultrafast electronic dynamics in quantum materials after photoexcitation.This paper reviews the development of a high-resolution time-and angle-resolved photoemission system based on nonlinear optical crystals and the studies on the ultrafast electronic dynamics in quantum materials using such a setup,including(1)probing the unoccupied electronic states in quantum materials,(2)photoinduced ultrafast electronic phase transitions,and(3)photoinduced new states of matter.展开更多
The gravitational redshift(GR),as predicted by Einstein’s general theory of relativity,posits that two identical clocks situated at different gravitational potentials will tick at different rates.In this study,we exp...The gravitational redshift(GR),as predicted by Einstein’s general theory of relativity,posits that two identical clocks situated at different gravitational potentials will tick at different rates.In this study,we explore the impact of the GR on a single-photon-based atom interferometer and propose a corresponding testing scheme.Our approach conceptualizes the atom interferometer as two coherent atomic clocks positioned at distinct elevations,which is referred to as an atomic clock interferometer,allowing us to derive the GR-induced phase shift.This effect becomes significant due to the notable energy difference between the two atomic internal states,comparable to other relativistic effects in single-photon-based atomic clock interferometers.Furthermore,our proposed scheme incorporates the velocity of the laser device to effectively mitigate other relativistic effects.The ensuing analysis indicates an anticipated GR test precision at the 10^(-5)level for our proposed approach.展开更多
The high tunability of two-dimensional(2D)materials makes them an optimal platform for simulating,achieving,and manipulating novel quantum states in condensed matter physics.Moire flatband systems formed through latti...The high tunability of two-dimensional(2D)materials makes them an optimal platform for simulating,achieving,and manipulating novel quantum states in condensed matter physics.Moire flatband systems formed through lattice mismatch or twisting between atomic layers have recently been discovered,allowing for bridging 2D materials with strongly correlated and topological physics.In this review,we briefly discuss band folding in graphene/hexagonal boron nitride(hBN)moire superlattices and related experimental results as well as introduce a general approach for developing 2D correlated systems and applying them in ABC trilayer graphene on hBN(ABC-TLG/hBN)moire superlattices.We also compare the experimental results of the tunable correlated and topological phenomenon of ABC-TLG/hBN with those of other related moire systems.展开更多
FeSe is one of the most enigmatic superconductors.Among the family of iron-based compounds,it has the simplest chemical makeup and structure,and yet it displays superconducting transition temperature(T_(c))spanning 0 ...FeSe is one of the most enigmatic superconductors.Among the family of iron-based compounds,it has the simplest chemical makeup and structure,and yet it displays superconducting transition temperature(T_(c))spanning 0 to 15 K for thin films,while it is typically 8 K for single crystals.This large variation of T_(c)within one family underscores a key challenge associated with understanding superconductivity in iron chalcogenides.Here,using a dual-beam pulsed laser deposition(PLD)approach,we have fabricated a unique lattice-constant gradient thin film of FeSe which has revealed a clear relationship between the atomic structure and the superconducting transition temperature for the first time.The dual-beam PLD that generates laser fluence gradient inside the plasma plume has resulted in a continuous variation in distribution of edge dislocations within a single film,and a precise correlation between the lattice constant and T_(c)has been observed here,namely,T_(c)∝√c-c_(0),where c is the c-axis lattice constant(and c_(0)is a constant).This explicit relation in conjunction with a theoretical investigation indicates that it is the shifting of the dxy orbital of Fe which plays a governing role in the interplay between nematicity and superconductivity in FeSe.展开更多
Two-dimensional(2D)Cr_((1+δ))Te_(2)materials exhibit strong magnetic ordering and high Curie temperatures,making them attractive for various applications.It is crucial to achieve controllable synthesis for their succ...Two-dimensional(2D)Cr_((1+δ))Te_(2)materials exhibit strong magnetic ordering and high Curie temperatures,making them attractive for various applications.It is crucial to achieve controllable synthesis for their successful integration into device technologies.In this study,we present the synthesis of phase-controllable 2D Cr_((1+δ))Te_(2)films on the Si(111)substrate via molecular beam epitaxy.The composition and phase transition of the as-grown Cr_((1+δ))Te_(2)films are characterized by using in-situ reflection high-energy electron diffraction,scanning tunneling microscopy,ex-situ X-ray photoelectron spectroscopy,X-ray diffraction,and theoretical calculations.At low growth temperatures,by carefully adjusting the film thickness from 2 to more than 3 layers,we achieve precise control over the phase of Cr_((1+δ))Te_(2),fromCrTe_(2)to Cr intercalated Cr_(2)Te_(3).At a relatively elevated growth temperature,it is demonstrated that the Cr_((1+δ))Te_(2)phase is independent of the film thickness,only Cr_(2)Te_(3)forms and its growth mode is thickness-dependent.These phase transitions at low growth temperatures and growth mode changes at elevated growth temperatures are attributed to interfacial effects and the phase stability of Cr_((1+δ))Te_(2)compounds.Additionally,we utilize scanning tunneling spectroscopy and computations to gain insights into the electronic properties of Cr_(2)Te_(3).The magnetic measurements reveal that the 30-nm Cr_(2)Te_(3)film exhibits ferromagnetic behavior with a Curie temperature of about 180 K.Our work offers a robust method for the controllable growth of high-quality 2D Cr_((1+δ))Te_(2)films on Si substrates,providing an ideal platform for investigating their intrinsic properties and advancing the development of 2D magnet-based spintronics devices.展开更多
Photons play essential roles in fundamental physics and practical technologies. They have become one of theattractive informaiton carriers for quantum computation and quantum simulation. Recently, various photonicdegr...Photons play essential roles in fundamental physics and practical technologies. They have become one of theattractive informaiton carriers for quantum computation and quantum simulation. Recently, various photonicdegrees of freedom supported by optical resonant cavities form photonic synthetic dimensions, which contribute toall-optical platforms for simulating novel topological materials. The photonic discrete or continuous degrees offreedom are mapped to the lattices or momenta of the simulated topological matter, and the couplings betweenoptical modes are equivalent to the interactions among quasi-particles. Mature optical modulations enable flexibleengineering of the simulated Hamiltonian. Meanwhile, the resonant detection methods provide direct approachesto obtaining the corresponding energy band structures, particle distributions and dynamical evolutions. In thisReview, we give an overview of the synthetic dimensions in optical cavities, including frequency, orbital angularmomentum, time-multiplexed lattice, and independent parameters. Abundant higher-dimensional topologicalmodels have been demonstrated in lower dimensional synthetic systems. We further discuss the potentialdevelopment of photonic synthetic dimensions in the future.展开更多
This review aims to provide a comprehensive overview of the development and current understanding of GaAs and InAs heterostructures,with a special emphasis on achieving high material quality and high-mobility two-dime...This review aims to provide a comprehensive overview of the development and current understanding of GaAs and InAs heterostructures,with a special emphasis on achieving high material quality and high-mobility two-dimensional electron gases(2DEGs).The review discusses the evolution of structural designs that have significantly contributed to the enhancement of electron mobility,highlighting the critical considerations of scattering mechanisms of the 2DEGs.In addition,this review examines the substantial contributions of Molecular Beam Epitaxy(MBE)to these developments,particularly through advancements in vacuum technology,source material purification,and precision control of growth conditions.The intent of this review is to serve as a useful reference for researchers and practitioners in the field,offering insights into the historical progression and technical details of these semiconductor systems.展开更多
Introducing superconductivity into two-dimensional(2D)films with nontrivial topology has been intensively pursued as one of the feasible scenarios to realize 1D topological superconductor.Prevailing endeavors mostly e...Introducing superconductivity into two-dimensional(2D)films with nontrivial topology has been intensively pursued as one of the feasible scenarios to realize 1D topological superconductor.Prevailing endeavors mostly exploit the external gating or proximity effect of a traditional superconductor,by which the critical temperatures(T_(c))are limited to several Kelvin range.Here,we report on the discovery of interface-enhanced superconductivity in monolayer 1T'-MoTe_(2) film.A thermally driven phase transition from Mo_(6)Te_(6) nanowires to 1T'-MoTe_(2) films,grown on SrTiO_(3)(001)surface by the molecular beam epitaxial methods,is demonstrated.A combined study of scanning tunneling microscopy/spectroscopy,electrical transport and magnetization measurements indicates the T_(c) of MoTe_(2) film is around 30 K,two orders of magnitude larger than its 3D counterpart crystal.This study shows that interfacial engineering is an efficient way to tune monolayer 1T'-MoTe_(2) film into superconducting states,and thus may pave the way toward higher-T_(c) 1D intrinsic topological superconductivity.展开更多
V_(3)Si,a classical silicide superconductor with relatively high T_(C)(∼16 K),is promising for constructing silicon-based superconducting devices and hetero-structures.However,real space characterization on its surfa...V_(3)Si,a classical silicide superconductor with relatively high T_(C)(∼16 K),is promising for constructing silicon-based superconducting devices and hetero-structures.However,real space characterization on its surfaces and superconducting properties are still limited.Here we report the first low-temperature scanning tunnelling microscopy(STM)study on cleaned V_(3)Si(111)single crystal surface.We observed a√3×√3 superstructure which displays mirror symmetry between adjacent terraces,indicating the surface is V-terminated and reconstructed.The tunneling spectrum shows full superconducting gap with double pairs of coherence peaks,but has a relatively small gap size with comparing to bulk T_(C).Impurity induced in-gap state is absent on surface defects but present on introduced magnetic adatoms.Upon applying magnetic field,a hexagonal vortex lattice is visualized.Interestingly,the vortex size is found to be field dependent,and the coherence length measured from single vortex at low field is significantly larger than estimated value from bulk H_(c2).These results reflect V_(3)Si is a multi-band,s-wave superconductor.展开更多
Connectivity between qubits plays an irreplaceable role in quantum computation.An urgent task of quantum computation based on atomic arrays is to generate effective coupling between two distant qubits,thereby enhancin...Connectivity between qubits plays an irreplaceable role in quantum computation.An urgent task of quantum computation based on atomic arrays is to generate effective coupling between two distant qubits,thereby enhancing connectivity.In this paper,we investigate the realization of two-qubit gates utilizing buffer-atomic configuration,where the non-coding atoms serve as quantum buses to connect the computational qubits.Geometric control is achieved through globally-shined laser pulses in the Rydberg blockade region.It is found that acceleration based on shortcut to adiabaticity can be realized by reshaping the original control waveforms.The proposed distant two-qubit gate demonstrates robustness against systematic errors and random noise.Further numerical simulations indicate that high-fidelity control is maintained even when considering next-nearest-neighbor coupling among the atoms.Thus,our proposal provides a fast and experimentally feasible method for realizing distant two-qubit gates in atomic arrays,which may contribute to improving the scalability of quantum computations.展开更多
Zero-energy modes localized at the ends of one-dimensional(1D)wires hold great potential as qubits for fault-tolerant quantum computing.However,all the candidates known to date exhibit a wave function that decays expo...Zero-energy modes localized at the ends of one-dimensional(1D)wires hold great potential as qubits for fault-tolerant quantum computing.However,all the candidates known to date exhibit a wave function that decays exponentially into the bulk and hybridizes with other nearby zero-modes,thus hampering their use for braiding operations.Here,we show that a quasi-1D diamond-necklace chain exhibits an unforeseen type of robust boundary state,namely compact localized zero-energy modes that do not decay into the bulk.We find that this state emerges due to the presence of a latent symmetry in the system.We experimentally realize the diamond-necklace chain in an electronic quantum simulator setup.展开更多
As we have known,the 20th century represents an era of quantum physics.Based on the quantum physics,the physics and technology of semiconductors andmicroelec-tronics,lasers and masers,superconductors and devices,etc.,...As we have known,the 20th century represents an era of quantum physics.Based on the quantum physics,the physics and technology of semiconductors andmicroelec-tronics,lasers and masers,superconductors and devices,etc.,have been developed rapidly and widely.These build the hardware for the information science and technology,which have become the main driving force behind the re-garded“third industrial revolution”.展开更多
A quantized Hall conductance(not conductivity)in three dimensions has been searched for more than 30 years.Here we explore it in 3D topological nodal-ring semimetals,by employing a minimal model describing the essenti...A quantized Hall conductance(not conductivity)in three dimensions has been searched for more than 30 years.Here we explore it in 3D topological nodal-ring semimetals,by employing a minimal model describing the essential physics.In particular,the bulk topology can be captured by a momentum-dependent winding number,which confines the drumhead surface states in a specific momentum region.This confinement leads to a surface quantum Hall conductance in a specific energy window in this 3D system.The winding number for the drumhead surface states and Chern number for their quantum Hall effect form a two-fold topological hierarchy.We demonstrate the one-to-one correspondence between the momentum-dependent winding number and wavefunction of the drumhead surface states.More importantly,we stress that breaking chiral symmetry is necessary for the quantum Hall effect of the drumhead surface states.The analytic theory can be verified numerically by the Kubo formula for the Hall conductance.We propose an experimental setup to distinguish the surface and bulk quantum Hall effects.The theory will be useful for ongoing explorations on nodal-ring semimetals.展开更多
Normal-mode splitting is a hallmark of strong coupling between two coupled harmonic oscillators.Here,we report the realization of strong coupling in the optically-levitated nanoparticle system via feedback.A silica na...Normal-mode splitting is a hallmark of strong coupling between two coupled harmonic oscillators.Here,we report the realization of strong coupling in the optically-levitated nanoparticle system via feedback.A silica nanoparticle is trapped by a tightly focused laser travelling in free space,which is regarded as a harmonic oscillators.An external electric oscillator is then phase-locked to the nanoparticle’s motion as another harmonic oscillator,which is modulated on the trapping laser to feedback and interact with the nanoparticle.Therefore,a highly manipulatable coupled-harmonic oscillator system is built in our platform and the normal-mode splitting is realized with strong coupling in both Hermitian and non-Hermitian cases.Moreover,since the coupling between the two harmonic oscillators induced by the feedback is flexibly manipulated,the normal-mode splitting following the cooling or heating effect is simultaneously observed.This method could be useful for further studying quantum mechanical Hamiltonian and non-Hermitian phenomena of an optically-levitated nanoparticle.展开更多
基金supported by the Basic Science Center Project of NSFC(grant no.52388201)the Ministry of Science and Technology of China(grant no.2023YFA1406400)+3 种基金the National Natural Science Foundation of China(grant no.12334003)the National Science Fund for Distinguished Young Scholars(grant no.12025405)the Beijing Advanced Innovation Center for Future Chip(ICFC)the Beijing Advanced Innovation Center for Materials Genome Engineering.
文摘Neural network force fields have significantly advanced ab initio atomistic simulations across diverse fields.However,their application in the realm of magnetic materials is still in its early stage due to challenges posed by the subtle magnetic energy landscape and the difficulty of obtaining training data.Here we introduce a data-efficient neural network architecture to represent density functional theory total energy,atomic forces,and magnetic forces as functions of atomic and magnetic structures.Our approach incorporates the principle of equivariance under the three-dimensional Euclidean group into the neural network model.Through systematic experiments on various systems,including monolayer magnets,curved nanotube magnets,and moiré-twisted bilayer magnets of CrI_(3),we showcase the method’s high efficiency and accuracy,as well as exceptional generalization ability.The work creates opportunities for exploring magnetic phenomena in large-scale materials systems.
基金supported by the Ministry of Science and Technology of China(Grant No.2022YFA1402700,2018YFGH000095)the NSF of China(Grant No.U2032213,11774223,12274186,11774352,11974244,U1832214,and U1932215)+2 种基金the interdisciplinary program Wuhan National High Magnetic Field Center(Grant No.WHMFC 202122)Huazhong University of Science and Technology,and the Research Grants Council of Hong Kong with General Research Fund Grant No.17303819the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33010100)。
文摘Spin-orbit coupling is an important ingredient to regulate the many-body physics,especially for many spin liquid candidate materials such as rare-earth magnets and Kitaev materials.The rare-earth chalcogenides NaYbCh_(2)(Ch=O,S,Se)is a congenital frustrating system to exhibit the intrinsic landmark of spin liquid by eliminating both the site disorders between Na+and Yb^(3+)ions with the big ionic size difference and the Dzyaloshinskii-Moriya interaction with the perfect triangular lattice of the Yb^(3+)ions.The temperature versus magnetic-field phase diagram is established by the magnetization,specific heat,and neutron-scattering measurements.Notably,the neutron diffraction spectra and the magnetization curve might provide microscopic evidence for a series of spin configuration for in-plane fields,which include the disordered spin liquid state,120°antiferromagnet,and one-half magnetization state.Furthermore,the ground state is suggested to be a gapless spin liquid from inelastic neutron scattering,and the magnetic field adjusts the spin orbit coupling.Therefore,the strong spin-orbit coupling in the frustrated quantum magnet substantially enriches low-energy spin physics.This rare-earth family could offer a good platform for exploring the quantum spin liquid ground state and quantum magnetic transitions.
基金support of the National Natural Science Foundation of China(Grant Nos.92365203,52072168,51861145201).
文摘The superconducting tunneling effect in heterostructures,describing the process where single electrons or Cooper pairs tunnel through the barrier,can always play a significant role in understanding the phase coherence and pairing mechanisms in superconductors.Taking advantage of the easy cleavage to atomically-thin monolayer structure of layered superconductors and resulting quantum confinement of electrons or Cooper pairs at two-dimensional limit,van der Waals superconducting materials hosting superconducting order in monolayers or heterostructures can exhibit extensive emergent phenomena associated with quantum phase transitions of vortex and anti-vortex pairs.Examples of superconducting tunnel junctions(STJs)based on layered superconductors have been demonstrated to achieve novel phenomena,including Andreev bound states,Majorana bound states and 0/π-phase junctions.Since the characteristic parameters of quasiparticle tunneling through the barrier are directly associated with the energy gap values of superconductors,such critical parameter can be obtained within the STJ device geometry,which helps us understand and control the pairing states and emerging phenomena in superconductors.In this review,from the perspective of STJs with single electron tunneling and Cooper pair tunneling,we discuss Andreev reflection,Majorana bound states,photon-induced tunneling effects,non-reciprocal transport and superconducting diode phenomena,as well as prospects for layered-superconductor-based STJs.
基金funding provided by Shanghai Jiao Tong Universitysupported by the Key R&D Plan of Shandong Province(Grant No.2021ZDPT01,2020CXGC010105)+5 种基金the National Key Research and Development(R&D)Plan of China(Grant No.2020YFA0309800)the Innovation Program for Quantum Science and Technology(2021ZD0300700)the National Natural Science Foundation of China(Grant Nos.T2125010,12174215,61971409 and 61971408)the Chinese Academy of Sciences,Shandong Provincial Natural Science Foundation(Grant Nos.ZR2020YQ45,ZR2022LLZ011)support from the Taishan Scholar Program of Shandong Provincsupport from the Youth Innovation Promotion Association(No.2019238).
文摘Quantum key distribution(QKD)holds the potential to establish secure keys over long distances.The distance of point-to-point QKD secure key distribution is primarily impeded by the transmission loss inherent to the channel.In the quest to realize a large-scale quantum network,increasing the QKD distance under current technology is of great research interest.Here we adopt the 3-intensity sending-or-not-sending twin-field QKD(TF-QKD)protocol with the actively-odd-parity-pairing method.The experiment demonstrates the feasibility of secure QKD over a 1002 km fibre channel considering the finite size effect.The secure key rate is 3.11×10^(–12)per pulse at this distance.Furthermore,by optimizing parameters for shorter fiber distances,we conducted performance tests on key distribution for fiber lengths ranging from 202 km to 505 km.Notably,the secure key rate for the 202 km,the normal distance between major cities,reached 111.74 kbps.
基金funding provided by Shanghai Jiao Tong Universityfunded by the National Natural Science Foundation of China(Grant Nos.U2330401 and 51790494).
文摘The profound impact of excited magnetic states on the intricate interplay between electron and lattice behaviors in magnetic materials is a topic of great interest.Unfortunately,despite the significant strides that have been made in first-principles methods,accurately tracking these phenomena remains a challenging and elusive task.The crux of the challenge that lies before us is centered on the intricate task of characterizing the magnetic configuration of an excited state,utilizing a first-principle approach that is firmly rooted in the ground state of the system.We propose a versatile self-adaptive spin-constrained density functional theory formalism.By iteratively optimizing the constraining field alongside the electron wave function during energy minimization,we are able to obtain an accurate potential energy surface that captures the longitudinal and transverse variations of magnetization in itinerant ferromagnetic Fe.Moreover,this technique allows us to identify the subtle coupling between magnetic moments and other degrees of freedom by tracking energy variation,providing new insights into the intricate interplay between magnetic interactions,electronic band structure,and phonon dispersion curves in single-layered CrI_(3).This new methodology represents a significant breakthrough in our ability to probe the complex and multifaceted properties of magnetic systems.
基金supported by the National Natural Science Foundation of China(NSFC)under Grants No.12188101,No.12322404,No.12104215,No.11834006the National Key R&D Program of China(Grant No.2022YFA1403601)+2 种基金Innovation Program for Quantum Science and Technology,2021ZD0301902F.T.was also supported by the Young Elite Scientists Sponsorship Program by the China Association for Science and TechnologyX.W.also acknowledges the support from the Tencent Foundation through the XPLORER PRIZE.
文摘Topological materials usually possess protected gapless states in either the boundary or bulk,exhibiting various properties such as spin-momentum locking,Klein tunneling,Fermi arcs and so on.Database searches using symmetry data at high-symmetry points have catalogued thousands of topological materials revealing a magnitude of band nodes(BNs)at high-symmetry points or lying within high-symmetry lines/planes.A complete mapping from symmetry data(namely,representation of little group)in any BN to the k·p model characterizing low-energy Hamiltonian around the BN(and from the k·p model to concrete BN,inversely),is expected to complete the characterization of all BNs and gapless states.Here we first review recent progress on classifying BNs by systematically and automatically constructing k·p models based on recently completed tabulation of all irreducible(co-)representation matrices of little groups of the 1651 magnetic space groups.As one indispensable input in constructing a symmetry-allowed and generic k·p model,the expansion order,has been carefully and systematically truncated for any BN to a reasonable nonzero integer,by comparing the emanating nodal structure(ENS,including nodal point,nodal line and nodal surface)near the BN obtained by the explicitly constructed k·p model and that by pure symmetry analysis using compatibility relations(CRs).Owing to the progress,we are able to summarize all 25 different configurations of ENS near BN required by CRs,provide a complete mapping from k·p model to its realization around BN,and the corresponding ENS by CRs in an accessible file,and also reveal the protection mechanism of additional nodal lines that escape conventional analysis by CRs and is only predictable by constructing k·p model.The symmetry-based classification results on all BNs could facilitate large-scale materials prediction and hold promise for realizing topological semimetals suitable for device applications.
基金support from the National Key R&D Program of China(Grants No.2021YFA1400202 and No.2021YFA1401800)National Natural Science Foundation of China(Grants No.11974243 and No.12141404)+1 种基金Natural Science Foundation of Shanghai(22ZR1479700)additional support from a Shanghai talent program.
文摘Upon femtosecond laser excitation in quantum materials,it is possible to study the many-body interactions through the non-equilibrium processes,realize ultrafast electronic phase transitions,and achieve photoinduced novel states or hidden states.Such studies of the interaction between the ultrafast laser and the quantum materials are the frontiers and attract significant research interests in the field of condensed matter physics.Time-and angle-resolved photoemission spectroscopy is a key experimental tool to study the ultrafast electronic dynamics in quantum materials after photoexcitation.This paper reviews the development of a high-resolution time-and angle-resolved photoemission system based on nonlinear optical crystals and the studies on the ultrafast electronic dynamics in quantum materials using such a setup,including(1)probing the unoccupied electronic states in quantum materials,(2)photoinduced ultrafast electronic phase transitions,and(3)photoinduced new states of matter.
基金supported by the National Natural Science Foundation of China(Grant No.11922404,11727809,12004128,12104174,12205110,and 12274613)。
文摘The gravitational redshift(GR),as predicted by Einstein’s general theory of relativity,posits that two identical clocks situated at different gravitational potentials will tick at different rates.In this study,we explore the impact of the GR on a single-photon-based atom interferometer and propose a corresponding testing scheme.Our approach conceptualizes the atom interferometer as two coherent atomic clocks positioned at distinct elevations,which is referred to as an atomic clock interferometer,allowing us to derive the GR-induced phase shift.This effect becomes significant due to the notable energy difference between the two atomic internal states,comparable to other relativistic effects in single-photon-based atomic clock interferometers.Furthermore,our proposed scheme incorporates the velocity of the laser device to effectively mitigate other relativistic effects.The ensuing analysis indicates an anticipated GR test precision at the 10^(-5)level for our proposed approach.
基金supported by National Key Research Program of China(grant nos.2020YFA0309000,2021YFA1400100)NSF of China(grant no.12174248)SJTU NO.21X010200846。
文摘The high tunability of two-dimensional(2D)materials makes them an optimal platform for simulating,achieving,and manipulating novel quantum states in condensed matter physics.Moire flatband systems formed through lattice mismatch or twisting between atomic layers have recently been discovered,allowing for bridging 2D materials with strongly correlated and topological physics.In this review,we briefly discuss band folding in graphene/hexagonal boron nitride(hBN)moire superlattices and related experimental results as well as introduce a general approach for developing 2D correlated systems and applying them in ABC trilayer graphene on hBN(ABC-TLG/hBN)moire superlattices.We also compare the experimental results of the tunable correlated and topological phenomenon of ABC-TLG/hBN with those of other related moire systems.
基金supported by the National Natural Science Foundation of China(12225412,12204333,12374141,11834016,11927808)the National Key Basic Research Program of China(2021YFA0718700,2022YFA1403900,2022YFA1403000)+4 种基金the Strategic Priority Research Program(B)of Chinese Academy of Sciences(XDB25000000,XDB33000000)Beijing Natural Science Foundation(Z190008),the Beijing Nova Program of Science and Technology(20220484014)CAS Project for Young Scientists in Basic Research(2022YSBR-048)The Key-Area Research and Development Program of Guangdong Province(Grant No.2020B0101340002)The work at the University of Maryland was funded by AFOSR FA9550-14-10332 and NIST 60NANB19D027.
文摘FeSe is one of the most enigmatic superconductors.Among the family of iron-based compounds,it has the simplest chemical makeup and structure,and yet it displays superconducting transition temperature(T_(c))spanning 0 to 15 K for thin films,while it is typically 8 K for single crystals.This large variation of T_(c)within one family underscores a key challenge associated with understanding superconductivity in iron chalcogenides.Here,using a dual-beam pulsed laser deposition(PLD)approach,we have fabricated a unique lattice-constant gradient thin film of FeSe which has revealed a clear relationship between the atomic structure and the superconducting transition temperature for the first time.The dual-beam PLD that generates laser fluence gradient inside the plasma plume has resulted in a continuous variation in distribution of edge dislocations within a single film,and a precise correlation between the lattice constant and T_(c)has been observed here,namely,T_(c)∝√c-c_(0),where c is the c-axis lattice constant(and c_(0)is a constant).This explicit relation in conjunction with a theoretical investigation indicates that it is the shifting of the dxy orbital of Fe which plays a governing role in the interplay between nematicity and superconductivity in FeSe.
基金funding provided by Shanghai Jiao Tong UniversityNSFC(Grants No.11790313,No.92065201,No.11874256,No.11874258,No.12074247,No.12174252 and No.11861161003)+3 种基金the Ministry of Science and Technology of China(Grants No.2019YFA0308600,2020YFA0309000)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Science and Technology Commission of Shanghai Municipality(Grants No.2019SHZDZX01,No.19JC1412701,No.20QA1405100)for financial supportfinancial support from Innovation program for Quantum Science and Technology(Grant No.2021ZD0302500).
文摘Two-dimensional(2D)Cr_((1+δ))Te_(2)materials exhibit strong magnetic ordering and high Curie temperatures,making them attractive for various applications.It is crucial to achieve controllable synthesis for their successful integration into device technologies.In this study,we present the synthesis of phase-controllable 2D Cr_((1+δ))Te_(2)films on the Si(111)substrate via molecular beam epitaxy.The composition and phase transition of the as-grown Cr_((1+δ))Te_(2)films are characterized by using in-situ reflection high-energy electron diffraction,scanning tunneling microscopy,ex-situ X-ray photoelectron spectroscopy,X-ray diffraction,and theoretical calculations.At low growth temperatures,by carefully adjusting the film thickness from 2 to more than 3 layers,we achieve precise control over the phase of Cr_((1+δ))Te_(2),fromCrTe_(2)to Cr intercalated Cr_(2)Te_(3).At a relatively elevated growth temperature,it is demonstrated that the Cr_((1+δ))Te_(2)phase is independent of the film thickness,only Cr_(2)Te_(3)forms and its growth mode is thickness-dependent.These phase transitions at low growth temperatures and growth mode changes at elevated growth temperatures are attributed to interfacial effects and the phase stability of Cr_((1+δ))Te_(2)compounds.Additionally,we utilize scanning tunneling spectroscopy and computations to gain insights into the electronic properties of Cr_(2)Te_(3).The magnetic measurements reveal that the 30-nm Cr_(2)Te_(3)film exhibits ferromagnetic behavior with a Curie temperature of about 180 K.Our work offers a robust method for the controllable growth of high-quality 2D Cr_((1+δ))Te_(2)films on Si substrates,providing an ideal platform for investigating their intrinsic properties and advancing the development of 2D magnet-based spintronics devices.
文摘Photons play essential roles in fundamental physics and practical technologies. They have become one of theattractive informaiton carriers for quantum computation and quantum simulation. Recently, various photonicdegrees of freedom supported by optical resonant cavities form photonic synthetic dimensions, which contribute toall-optical platforms for simulating novel topological materials. The photonic discrete or continuous degrees offreedom are mapped to the lattices or momenta of the simulated topological matter, and the couplings betweenoptical modes are equivalent to the interactions among quasi-particles. Mature optical modulations enable flexibleengineering of the simulated Hamiltonian. Meanwhile, the resonant detection methods provide direct approachesto obtaining the corresponding energy band structures, particle distributions and dynamical evolutions. In thisReview, we give an overview of the synthetic dimensions in optical cavities, including frequency, orbital angularmomentum, time-multiplexed lattice, and independent parameters. Abundant higher-dimensional topologicalmodels have been demonstrated in lower dimensional synthetic systems. We further discuss the potentialdevelopment of photonic synthetic dimensions in the future.
基金supported by National Natural Science Foundation of China(92065206)the Innovation Program for Quantum Science and Technology(2021ZD0302400).
文摘This review aims to provide a comprehensive overview of the development and current understanding of GaAs and InAs heterostructures,with a special emphasis on achieving high material quality and high-mobility two-dimensional electron gases(2DEGs).The review discusses the evolution of structural designs that have significantly contributed to the enhancement of electron mobility,highlighting the critical considerations of scattering mechanisms of the 2DEGs.In addition,this review examines the substantial contributions of Molecular Beam Epitaxy(MBE)to these developments,particularly through advancements in vacuum technology,source material purification,and precision control of growth conditions.The intent of this review is to serve as a useful reference for researchers and practitioners in the field,offering insights into the historical progression and technical details of these semiconductor systems.
基金funding provided by Shanghai Jiao Tong UniversityNational Natural Science Foundation of China(Grants No.11790313,No.92065201,No.11874256,No.11874258,No.12074247,No.12174252 and No.11861161003)+3 种基金the Ministry of Science and Technology of China(Grants No.2019YFA0308600,2020YFA0309000)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Science and Technology Commission of Shanghai Municipality(Grants No.2019SHZDZX01,No.19JC1412701,No.20QA1405100)for financial supportfinancial support from Innovation program for Quantum Science and Technology(Grant No.2021ZD0302500).
文摘Introducing superconductivity into two-dimensional(2D)films with nontrivial topology has been intensively pursued as one of the feasible scenarios to realize 1D topological superconductor.Prevailing endeavors mostly exploit the external gating or proximity effect of a traditional superconductor,by which the critical temperatures(T_(c))are limited to several Kelvin range.Here,we report on the discovery of interface-enhanced superconductivity in monolayer 1T'-MoTe_(2) film.A thermally driven phase transition from Mo_(6)Te_(6) nanowires to 1T'-MoTe_(2) films,grown on SrTiO_(3)(001)surface by the molecular beam epitaxial methods,is demonstrated.A combined study of scanning tunneling microscopy/spectroscopy,electrical transport and magnetization measurements indicates the T_(c) of MoTe_(2) film is around 30 K,two orders of magnitude larger than its 3D counterpart crystal.This study shows that interfacial engineering is an efficient way to tune monolayer 1T'-MoTe_(2) film into superconducting states,and thus may pave the way toward higher-T_(c) 1D intrinsic topological superconductivity.
基金supported by the Innovation Program for Quantum Science and Technology(Grant no.2021ZD0302800)National Natural Science Foundation of China(Grants Nos.92065202,11888101,11790312,11961160717,12225403)+2 种基金Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Science and Technology Commission of Shanghai Municipality,China(Grant No.21TQ1400100)funding provided by Shanghai Jiao Tong University.
文摘V_(3)Si,a classical silicide superconductor with relatively high T_(C)(∼16 K),is promising for constructing silicon-based superconducting devices and hetero-structures.However,real space characterization on its surfaces and superconducting properties are still limited.Here we report the first low-temperature scanning tunnelling microscopy(STM)study on cleaned V_(3)Si(111)single crystal surface.We observed a√3×√3 superstructure which displays mirror symmetry between adjacent terraces,indicating the surface is V-terminated and reconstructed.The tunneling spectrum shows full superconducting gap with double pairs of coherence peaks,but has a relatively small gap size with comparing to bulk T_(C).Impurity induced in-gap state is absent on surface defects but present on introduced magnetic adatoms.Upon applying magnetic field,a hexagonal vortex lattice is visualized.Interestingly,the vortex size is found to be field dependent,and the coherence length measured from single vortex at low field is significantly larger than estimated value from bulk H_(c2).These results reflect V_(3)Si is a multi-band,s-wave superconductor.
基金supported by the National Natural Science Foundation of China(Grants No.12225405,No.U20A2074,No.12304287,No.12074180,No.12074132 and No.12304287)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301700)+3 种基金the National Key Research and Development Program of China(Grant No.2022YFA1405300)the Project funded by China Postdoctoral Science Foundation(Grant No.2022M721222,No.2023T160233)Guangdong Basic and Applied Basic Research Foundation(Grants No.2023A1515011550 and No.2024A1515012516)Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDZX2304002,No.GDZX2303006).
文摘Connectivity between qubits plays an irreplaceable role in quantum computation.An urgent task of quantum computation based on atomic arrays is to generate effective coupling between two distant qubits,thereby enhancing connectivity.In this paper,we investigate the realization of two-qubit gates utilizing buffer-atomic configuration,where the non-coding atoms serve as quantum buses to connect the computational qubits.Geometric control is achieved through globally-shined laser pulses in the Rydberg blockade region.It is found that acceleration based on shortcut to adiabaticity can be realized by reshaping the original control waveforms.The proposed distant two-qubit gate demonstrates robustness against systematic errors and random noise.Further numerical simulations indicate that high-fidelity control is maintained even when considering next-nearest-neighbor coupling among the atoms.Thus,our proposal provides a fast and experimentally feasible method for realizing distant two-qubit gates in atomic arrays,which may contribute to improving the scalability of quantum computations.
基金financial support from the European Research Council(Horizon 2020“FRACTAL”,865570)the Dutch Research Council(grant 16PR3245)+2 种基金the research program“Materials for the Quantum Age”(QuMat)for financial supportThis program(registration number 024.005.006)is part of the Gravitation program financed by the Dutch Ministry of Education,Culture and Science(OCW)funding provided by Shanghai Jiao Tong University.
文摘Zero-energy modes localized at the ends of one-dimensional(1D)wires hold great potential as qubits for fault-tolerant quantum computing.However,all the candidates known to date exhibit a wave function that decays exponentially into the bulk and hybridizes with other nearby zero-modes,thus hampering their use for braiding operations.Here,we show that a quasi-1D diamond-necklace chain exhibits an unforeseen type of robust boundary state,namely compact localized zero-energy modes that do not decay into the bulk.We find that this state emerges due to the presence of a latent symmetry in the system.We experimentally realize the diamond-necklace chain in an electronic quantum simulator setup.
文摘As we have known,the 20th century represents an era of quantum physics.Based on the quantum physics,the physics and technology of semiconductors andmicroelec-tronics,lasers and masers,superconductors and devices,etc.,have been developed rapidly and widely.These build the hardware for the information science and technology,which have become the main driving force behind the re-garded“third industrial revolution”.
基金supported by the National Key R&D Program of China(2022YFA1403700)the Innovation Program for Quantum Science and Technology(2021ZD0302400)+3 种基金the National Natural Science Foundation of China(11925402,11534001,and 11974249)Guangdong province(2020KCXTD001 and 2016ZT06D348)the Natural Science Foundation of Shanghai(19ZR1437300)supported by Center for Computational Science and Engineering of SUSTech.
文摘A quantized Hall conductance(not conductivity)in three dimensions has been searched for more than 30 years.Here we explore it in 3D topological nodal-ring semimetals,by employing a minimal model describing the essential physics.In particular,the bulk topology can be captured by a momentum-dependent winding number,which confines the drumhead surface states in a specific momentum region.This confinement leads to a surface quantum Hall conductance in a specific energy window in this 3D system.The winding number for the drumhead surface states and Chern number for their quantum Hall effect form a two-fold topological hierarchy.We demonstrate the one-to-one correspondence between the momentum-dependent winding number and wavefunction of the drumhead surface states.More importantly,we stress that breaking chiral symmetry is necessary for the quantum Hall effect of the drumhead surface states.The analytic theory can be verified numerically by the Kubo formula for the Hall conductance.We propose an experimental setup to distinguish the surface and bulk quantum Hall effects.The theory will be useful for ongoing explorations on nodal-ring semimetals.
基金supported by National Natural Science Foundation of China(Grant No.11234008,11361161002,61975101,61571276,11654002).
文摘Normal-mode splitting is a hallmark of strong coupling between two coupled harmonic oscillators.Here,we report the realization of strong coupling in the optically-levitated nanoparticle system via feedback.A silica nanoparticle is trapped by a tightly focused laser travelling in free space,which is regarded as a harmonic oscillators.An external electric oscillator is then phase-locked to the nanoparticle’s motion as another harmonic oscillator,which is modulated on the trapping laser to feedback and interact with the nanoparticle.Therefore,a highly manipulatable coupled-harmonic oscillator system is built in our platform and the normal-mode splitting is realized with strong coupling in both Hermitian and non-Hermitian cases.Moreover,since the coupling between the two harmonic oscillators induced by the feedback is flexibly manipulated,the normal-mode splitting following the cooling or heating effect is simultaneously observed.This method could be useful for further studying quantum mechanical Hamiltonian and non-Hermitian phenomena of an optically-levitated nanoparticle.
