Superconducting diodes,which enable dissipationless supercurrent flow in one direction while blocking it in the reverse direction,are emerging as pivotal components for superconducting electronics.The development of e...Superconducting diodes,which enable dissipationless supercurrent flow in one direction while blocking it in the reverse direction,are emerging as pivotal components for superconducting electronics.The development of editable superconducting diodes could unlock transformative applications,including dynamically reconfigurable quantum circuits that adapt to operational requirements.Here,we report the first observation of the superconducting diode effect(SDE)in LaAlO_(3)/KTaO_(3) heterostructures—a two-dimensional oxide interface superconductor with exceptional tunability.We observe a strong SDE in Hall-bar(or strip-shaped)devices under perpendicular magnetic fields(<15 Oe),with efficiencies above 40%and rectification signals exceeding 10 mV.Through conductive atomic force microscope lithography,we demonstrate reversible nanoscale editing of the SDE’s polarity and efficiency by locally modifying the superconducting channel edges.This approach enables multiple nonvolatile configurations within a single device,realizing an editable superconducting diode.Our work establishes LaAlO_(3)/KTaO_(3) as a platform for vortex-based nonreciprocal transport and provides a pathway toward designer quantum circuits with on-demand functionalities.展开更多
Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and ...Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.展开更多
We report a comprehensive investigation of the superconducting properties of the mineral superconductor covellite(Cu S)using high-quality single crystals.First,we establish that Cu S is an intrinsic type-Ⅱsuperconduc...We report a comprehensive investigation of the superconducting properties of the mineral superconductor covellite(Cu S)using high-quality single crystals.First,we establish that Cu S is an intrinsic type-Ⅱsuperconductor,correcting its long-standing classification as type-Ⅰ.Second,a complete set of anisotropic superconducting parameters is determined,including the critical fields,penetration depth and coherence length,which yield a Ginzburg–Landau parameterκ~1.5 and a moderate anisotropy ofγ~2.Our results indicate that this type-Ⅱsuperconductivity can be well-described by a conventional,weak-coupling,single-band s-wave pairing mechanism.This work fills a long-standing gap in the understanding of this archetypal superconductor.展开更多
We present a systematic investigation of the superconductivity in high-quality CsTi_(3)Bi_(5) single crystals by combining bulk property characterization and local-probe spectroscopy.Two successive superconducting tra...We present a systematic investigation of the superconductivity in high-quality CsTi_(3)Bi_(5) single crystals by combining bulk property characterization and local-probe spectroscopy.Two successive superconducting transitions are observed in this newly discovered kagome material.In the first stage,the diamagnetic response strengthens significantly from T_(c)~4.9 K to 4.6 K,followed by a broad transition below 4.6 K in the second stage.Moreover,different magnetic field dependences are observed for the two stages,where the first stage is field-insensitive while the second stage exhibits strong field dependence.The ultra-low magnetic field measurements indicate that the lower critical field H_(c1)(T)exhibits small anisotropy.Based on a comparative study of the superconducting state in CsBi2 and microscopic verification via scanning tunneling microscopy(STM),our results suggest the emergence of exotic and intrinsic superconductivity in this new titanium-based kagome superconductor,establishing it as a promising platform for further exploring the complexity of electronic states in the kagome lattice.展开更多
A solenoid is typically used in normally conducting and superconducting radio frequency(SRF)photoinjectors to compensate for the projected transverse beam emittance.In the ELBE SRF Gun-Ⅱ,a superconducting solenoid is...A solenoid is typically used in normally conducting and superconducting radio frequency(SRF)photoinjectors to compensate for the projected transverse beam emittance.In the ELBE SRF Gun-Ⅱ,a superconducting solenoid is positioned inside the gun cryomodule approximately 0.7 m from the end of the gun cavity.The spherical aberration and multipole field effects caused by offset and tilt limit the reduction in beam emittance for high bunch charges.We designed a novel superconducting(SC)solenoid with a lower spherical aberration coefficient.In the simulation,the beam emittance from the spherical aberration decreased by 47%.Both the longitudinal and transverse fields were measured and analyzed using the formalism fitting method to assess the performance of the SC solenoid within the cryomodule and its influence on the beam transverse emittance.展开更多
This study investigates the effect of BaHfO_(3)(BHO)addition on the optical properties of YBa_2Cu_(3)O_(7-δ)(YBCO)superconducting thin films using spectroscopic ellipsometry.Through Raman spectroscopy and SEM analysi...This study investigates the effect of BaHfO_(3)(BHO)addition on the optical properties of YBa_2Cu_(3)O_(7-δ)(YBCO)superconducting thin films using spectroscopic ellipsometry.Through Raman spectroscopy and SEM analysis,optimal 10-min Ar ion etching effectively removes surface a-axis-oriented grains and Ba–Cu–O impurities,enhancing surface quality.Optical conductivity analysis reveals a doping-dependent evolution:10%BHO doping maximizes free carrier density and interband transition efficiency,attributed to optimized Cu–O bond contraction and reduced lattice distortions.Higher doping induces defect clustering,carrier scattering,and redshifted transitions due to lattice expansion.Dielectric function and loss function analyses confirm enhanced plasmonic behavior and flux pinning at 10%doping,while excessive doping degrades electronic transitions.These results highlight the critical role of controlled BHO addition and surface treatment in tailoring the optical and superconducting properties of YBCO,offering insights into the interplay among doping,carrier dynamics,and electronic structure in high-temperature superconductors(HTS).展开更多
Superconductivity in two-dimensional(2D)materials has attracted considerable attention due to their unique physical properties and potential for high-temperature operation.Boron-based 2D compounds are particularly pro...Superconductivity in two-dimensional(2D)materials has attracted considerable attention due to their unique physical properties and potential for high-temperature operation.Boron-based 2D compounds are particularly promising,thanks to their structural flexibility and the emergence of strong electron-phonon coupling(EPC)associated with light elements.While most previous studies have focused on stabilizing boron sheets through metal incorporation,we propose an alternative approach based on multicenter bonding enabled by group-IV non-metallic elements(Si,Ge,Sn).The resulting XB_(2)(X=Si,Ge,Sn)monolayers,which adopt a MgB_(2)-like monolayer configuration,are stabilized by a seven-center two-electron(7c-2e)bonding network between the X atoms and the boron honeycomb lattice.This bonding lowers the energy of the B-p_(z)orbitals and enhances lattice stability.The superconducting transition temperature(T_(c))increases significantly with the atomic number of X—from 4.7 K in SiB_(2)to 13.3 K in GeB_(2)and 24.9 K in SnB_(2)—driven by an increased carrier density near the Fermi level(E_(F))and softening of the high-frequency E_(2)phonon mode.Furthermore,we design a SnB_4 monolayer,in which a Sn layer is sandwiched between the two boron layers.This structure enriches in-plane phonon modes and strengthens EPC,yielding a T_(c)of 38 K,close to the McMillan limit.These findings highlight the critical role of multicenter bonding and targeted phonon engineering in enabling high-T_(c)2D boron-based superconductors.展开更多
In recent years,the research on superconductivity in one-dimensional(1D)materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices.However,the critical temperat...In recent years,the research on superconductivity in one-dimensional(1D)materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices.However,the critical temperature(T_(c))of 1D superconductors is low.In this work,we theoretically investigate the possible high T_(c) superconductivity of(5,5)carbon nanotube(CNT).The pristine(5,5)CNT is a Dirac semimetal and can be modulated into a semiconductor by full hydrogenation.Interestingly,by further hole doping,it can be regulated into a metallic state with the sp^(3)-hybridized σ electrons metalized,and a giant Kohn anomaly appears in the optical phonons.The two factors together enhance the electron–phonon coupling,and lead to high-T_(c) superconductivity.When the hole doping concentration of hydrogenated-(5,5)CNT is 2.5 hole/cell,the calculated T_(c) is 82.3 K,exceeding the boiling point of liquid nitrogen.Therefore,the predicted hole-doped hydrogenated-(5,5)CNT provides a new platform for 1D high-T_(c) superconductivity and may have potential applications in 1D nanodevices.展开更多
Interfacial superconductivity(IS)has been a topic of intense interest in condensed matter physics,due to its unique properties and exotic photoelectrical performance.However,there are few reports about IS systems cons...Interfacial superconductivity(IS)has been a topic of intense interest in condensed matter physics,due to its unique properties and exotic photoelectrical performance.However,there are few reports about IS systems consisting of two insulators.Here,motivated by the emergence of an insulator-metal transition in type-Ⅲ heterostructures and the superconductivity in some“special”two-dimensional(2D)semiconductors via electron doping,we predict that the 2D heterostructure SnSe_(2)/PtTe_(2) is a model system for realizing IS by using firstprinciples calculations.Our results show that due to slight but crucial interlayer charge transfer,SnSe_(2)/PtTe_(2) turns to be a type-Ⅲ heterostructure with metallic properties and shows a superconducting transition with the critical temperature(T_(c))of 3.73 K.Similar to the enhanced electron–phonon coupling(EPC)in the electrondoped SnSe_(2) monolayer,the IS in the SnSe_(2)/PtTe_(2) heterostructure mainly originates from the metallized SnSe_(2) layer.Furthermore,we find that its superconductivity is sensitive to tensile lattice strain,forming a domeshaped superconducting phase diagram.Remarkably,at 7%biaxial tensile strain,the superconducting T_(c) can increase more than twofold(8.80 K),resulting from softened acoustic phonons at the𝑀point and enhanced EPC strength.Our study provides a concrete example for realizing IS in type-Ⅲ heterostructures,which waits for future experimental verification.展开更多
High-pressure electrides,characterized by the presence of interstitial quasi-atoms(ISQs),possess unique electronic structures and physical properties,such as diverse dimensions of electride states exhibiting different...High-pressure electrides,characterized by the presence of interstitial quasi-atoms(ISQs),possess unique electronic structures and physical properties,such as diverse dimensions of electride states exhibiting different superconductivity,which has attracted significant attention.Here,we report a new electron-deficient type of electride Li_(4)Al and identify its phase transition progress with pressurization,where the internal driving force behind phase transitions,bonding characteristics,and superconducting behaviors have been revealed based on first-principles density functional theory.Through analysis of the bonding properties of electride Li_(4)Al,we demonstrate that the ISQs exhibiting increasingly covalent characteristics between Al ions play a critical role in driving the phase transition.Our electron–phonon coupling calculations indicate that all phases exhibit superconducting behaviors.Importantly,we prove that the ISQs behave as free electrons and demonstrate that the factor governing T_(c) is primarily derived from Li-p-hybridized electronic states with ISQ compositions.These electronic states are scattered by low-frequency phonons arising from mixed vibrations of Li and Al affected by ISQs to enhance electron–phonon coupling.Our study largely expands the research scope of electrides,provides new insight for understanding phase transitions,and elucidates the effects of ISQs on superconducting behavior.展开更多
Motivated by the recent discovery of superconductivity in the kagome metal CsCr_(3)Sb_(5) under pressure,we theoretically investigate the superconducting pairing symmetry and the impact of spin–orbit coupling(SOC)in ...Motivated by the recent discovery of superconductivity in the kagome metal CsCr_(3)Sb_(5) under pressure,we theoretically investigate the superconducting pairing symmetry and the impact of spin–orbit coupling(SOC)in this system.By employing an effective four-orbital tight-binding model and solving the linearized gap equation within the random phase approximation,we find that the large inter-orbital spin fluctuations enhanced by Hund’s coupling promote a superconducting gap function with E_(2g)symmetry.The inclusion of SOC further stabilizes this gap symmetry.Our analysis also reveals that the d_(x^(2)-y^(2))orbital plays the dominant role in forming the superconducting pairs.展开更多
We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X...We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X represents transition metal elements.Systematic analysis of electronic band structures,phonon dispersions,and electron-phonon coupling reveals that substitution of MA binary metal combinations and X metal atoms can create favorable conditions for superconductivity.Mapping of superconducting critical temperatures,combined with dynamical stability analysis through phonon calculations,identifies ten superconducting candidates at ambient pressure.Among these,LiNaAgH_(6) exhibits nearly-free-electron behavior reminiscent of monovalent electron superconductors.It demonstrates exceptional superconducting properties with electron–phonon coupling λ=2.707,which yields a superconducting transition temperature T_(c) of 206.4 K using the Allen–Dynes formula.Its structural analogs MgNaPdH_(6),LiMgPdH_(6),LiMgAgH_(6),LiMgAuH_(6) all exhibit superconducting transition temperatures above 110 K.These findings advance our fundamental understanding of superconductivity in quaternary hydrides and provide guidance for rational design of new high-temperature superconducting materials.展开更多
Applied field magnetoplasmadynamic thrusters(AF-MPDTs), with their high specific impulse and considerable thrust, are increasingly favored for large-scale space missions. This paper presents the composition, functiona...Applied field magnetoplasmadynamic thrusters(AF-MPDTs), with their high specific impulse and considerable thrust, are increasingly favored for large-scale space missions. This paper presents the composition, functionality, and testing methods of a high-power electric propulsion performance testing system, along with the vacuum ignition test results of a 100 kW superconducting MPD thruster. The relationships between thruster efficiency, magnetic field strength, current,and mass flow rate are analyzed. For each combination of current and flow rate in an AF-MPDT, there is an optimal magnetic field strength where the thruster efficiency reaches its peak. Under conditions of 320 A current and 60 mg/s flow rate,the optimal magnetic field strength is 0.5 T, yielding the highest thruster efficiency of 71%.展开更多
Conventional superconducting nanowire single-photon detectors(SNSPDs)have been typically limited in their applications due to their size,weight,and power consumption,which confine their use to laboratory settings.Howe...Conventional superconducting nanowire single-photon detectors(SNSPDs)have been typically limited in their applications due to their size,weight,and power consumption,which confine their use to laboratory settings.However,with the rapid development of remote imaging,sensing technologies,and long-range quantum communication with fewer topographical constraints,the demand for high-efficiency single-photon detectors integrated with avionic platforms is rapidly growing.We herein designed and manufactured the first drone-based SNSPD system with a system detection efficiency(SDE)as high as 91.8%.This drone-based system incorporates high-performance NbTiN SNSPDs,a self-developed miniature liquid helium dewar,and custom-built integrated electrical setups,making it capable of being launched in complex topographical conditions.Such a drone-based SNSPD system may open the use of SNSPDs for applications that demand high SDE in complex environments.展开更多
In the 9 December 2024 issue of Nature[1],a team of Google engineers reported breakthrough results using“Willow”,their lat-est quantum computing chip(Fig.1).By meeting a milestone“below threshold”reduction in the ...In the 9 December 2024 issue of Nature[1],a team of Google engineers reported breakthrough results using“Willow”,their lat-est quantum computing chip(Fig.1).By meeting a milestone“below threshold”reduction in the rate of errors that plague super-conducting circuit-based quantum computing systems(Fig.2),the work moves the field another step towards its promised super-charged applications,albeit likely still many years away.Areas expected to benefit from quantum computing include,among others,drug discovery,materials science,finance,cybersecurity,and machine learning.展开更多
Research on the mechanical–electrical properties is crucial for designing and preparing high-temperature superconducting(HTS)cables.Various winding core structures can influence the mechanical–electrical behavior of...Research on the mechanical–electrical properties is crucial for designing and preparing high-temperature superconducting(HTS)cables.Various winding core structures can influence the mechanical–electrical behavior of cables,but the impact of alterations in the winding core structure on the mechanical–electrical behavior of superconducting cables remains unclear.This paper presents a 3D finite element model to predict the performance of three cables with different core structures when subjected to transverse compression and axial tension.The three cables analyzed are CORC(conductor-on-round-core),CORT(conductor-on-round-tube),and HFRC(conductor-on-spiral-tube).A parametric analysis is carried out by varying the core diameter and inner-to-outer diameter ratio.Results indicate that the CORT cable demonstrates better performance in transverse compression compared to the CORC cable,aligning with experimental data.Among the three cables,the HFRC cables exhibit the weakest resistance to transverse deformation.However,the HFRC cable demonstrates superior tensile deformation resistance compared to the CORT cable,provided that the transverse compression properties are maintained.Finite element results also show that the optimum inner-to-outer diameter ratios for achieving the best transverse compression performance are approximately 0.8 for CORT cables and 0.6 for HFRC cables.Meanwhile,the study explores the effect of structural changes in HTS cable winding cores on their electromagnetic properties.It recommends utilizing small tape gaps,lower frequencies,and spiral core construction to minimize eddy losses.The findings presented in this paper offer valuable insights for the commercialization and practical manufacturing of HTS cables.展开更多
Superconducting radio-frequency(SRF)cavities are the core components of SRF linear accelerators,making their stable operation considerably important.However,the operational experience from different accelerator labora...Superconducting radio-frequency(SRF)cavities are the core components of SRF linear accelerators,making their stable operation considerably important.However,the operational experience from different accelerator laboratories has revealed that SRF faults are the leading cause of short machine downtime trips.When a cavity fault occurs,system experts analyze the time-series data recorded by low-level RF systems and identify the fault type.However,this requires expertise and intuition,posing a major challenge for control-room operators.Here,we propose an expert feature-based machine learning model for automating SRF cavity fault recognition.The main challenge in converting the"expert reasoning"process for SRF faults into a"model inference"process lies in feature extraction,which is attributed to the associated multidimensional and complex time-series waveforms.Existing autoregression-based feature-extraction methods require the signal to be stable and autocorrelated,resulting in difficulty in capturing the abrupt features that exist in several SRF failure patterns.To address these issues,we introduce expertise into the classification model through reasonable feature engineering.We demonstrate the feasibility of this method using the SRF cavity of the China accelerator facility for superheavy elements(CAFE2).Although specific faults in SRF cavities may vary across different accelerators,similarities exist in the RF signals.Therefore,this study provides valuable guidance for fault analysis of the entire SRF community.展开更多
The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry ...The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry and can significantly enhance the energy efficiency of aircraft propulsion system.Electric motor is the most critical electromechanical energy conversion component in an aircraft electric propulsion system(EPS).High-performance electric motors,power electronic converters and EPS control form the foundation of the EPA.This paper provides an overview of the characteristics of electric motors for EPA,analyzes the inverter topologies of EPSs,and reviews ongoing EPA projects.The article highlights the latest advancements in three types of motors:superconducting motors(SCMs),permanent magnet synchronous motors(PMSMs),and induction motors(IMs).It summarizes the control system architectures of current EPA initiatives and,building on this foundation,proposes future research directions for EPSs.These include cutting-edge areas such as high-performance motors and advanced manufacturing technologies,Ga N-or Si C-based inverter integration and innovation,electric propulsion control systems,and optimization of wiring systems.展开更多
Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes dev...Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.展开更多
基金supported by the National Key R&D Program of China (Grant No.2023YFA1406400)the National Natural Science Foundation of China (Grant Nos.12534005 and 12325402)。
文摘Superconducting diodes,which enable dissipationless supercurrent flow in one direction while blocking it in the reverse direction,are emerging as pivotal components for superconducting electronics.The development of editable superconducting diodes could unlock transformative applications,including dynamically reconfigurable quantum circuits that adapt to operational requirements.Here,we report the first observation of the superconducting diode effect(SDE)in LaAlO_(3)/KTaO_(3) heterostructures—a two-dimensional oxide interface superconductor with exceptional tunability.We observe a strong SDE in Hall-bar(or strip-shaped)devices under perpendicular magnetic fields(<15 Oe),with efficiencies above 40%and rectification signals exceeding 10 mV.Through conductive atomic force microscope lithography,we demonstrate reversible nanoscale editing of the SDE’s polarity and efficiency by locally modifying the superconducting channel edges.This approach enables multiple nonvolatile configurations within a single device,realizing an editable superconducting diode.Our work establishes LaAlO_(3)/KTaO_(3) as a platform for vortex-based nonreciprocal transport and provides a pathway toward designer quantum circuits with on-demand functionalities.
基金supported by the National Natural Science Foundation of China(Grant Nos.12222413,12174443,12274459,and 12404266)the National Key R&D Program of China(Grant Nos.2023YFA1406500,2022YFA1403800,and 2022YFA1403103)+3 种基金the Natural Science Foundation of Shanghai (Grant No.23ZR1482200)the Natural Science Foundation of Ningbo (Grant No.2024J019)the Science Research Project of Hebei Education Department (Grant No.BJ2025060)the funding of Ningbo Yongjiang Talent Program。
文摘Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1611102,2022YFA1403903,2022YFA1602802,and 2023YFA1406101)the National Natural Science Foundation of China(Grant No.12304075)CAS Project for Young Scientists in Basic Research(Grant No.2022YSBR-048)。
文摘We report a comprehensive investigation of the superconducting properties of the mineral superconductor covellite(Cu S)using high-quality single crystals.First,we establish that Cu S is an intrinsic type-Ⅱsuperconductor,correcting its long-standing classification as type-Ⅰ.Second,a complete set of anisotropic superconducting parameters is determined,including the critical fields,penetration depth and coherence length,which yield a Ginzburg–Landau parameterκ~1.5 and a moderate anisotropy ofγ~2.Our results indicate that this type-Ⅱsuperconductivity can be well-described by a conventional,weak-coupling,single-band s-wave pairing mechanism.This work fills a long-standing gap in the understanding of this archetypal superconductor.
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1611102,2022YFA1403903,2023YFA1406101,and 2022YFA1204100)the National Natural Science Foundation of China(Grant Nos.12304075 and 62488201)+1 种基金CAS Project for Young Scientists in Basic Research(Grant Nos.2022YSBR-048 and YSBR-003)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘We present a systematic investigation of the superconductivity in high-quality CsTi_(3)Bi_(5) single crystals by combining bulk property characterization and local-probe spectroscopy.Two successive superconducting transitions are observed in this newly discovered kagome material.In the first stage,the diamagnetic response strengthens significantly from T_(c)~4.9 K to 4.6 K,followed by a broad transition below 4.6 K in the second stage.Moreover,different magnetic field dependences are observed for the two stages,where the first stage is field-insensitive while the second stage exhibits strong field dependence.The ultra-low magnetic field measurements indicate that the lower critical field H_(c1)(T)exhibits small anisotropy.Based on a comparative study of the superconducting state in CsBi2 and microscopic verification via scanning tunneling microscopy(STM),our results suggest the emergence of exotic and intrinsic superconductivity in this new titanium-based kagome superconductor,establishing it as a promising platform for further exploring the complexity of electronic states in the kagome lattice.
基金Open Access funding enabled and organized by Projekt DEAL.
文摘A solenoid is typically used in normally conducting and superconducting radio frequency(SRF)photoinjectors to compensate for the projected transverse beam emittance.In the ELBE SRF Gun-Ⅱ,a superconducting solenoid is positioned inside the gun cryomodule approximately 0.7 m from the end of the gun cavity.The spherical aberration and multipole field effects caused by offset and tilt limit the reduction in beam emittance for high bunch charges.We designed a novel superconducting(SC)solenoid with a lower spherical aberration coefficient.In the simulation,the beam emittance from the spherical aberration decreased by 47%.Both the longitudinal and transverse fields were measured and analyzed using the formalism fitting method to assess the performance of the SC solenoid within the cryomodule and its influence on the beam transverse emittance.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52172271,12374378,52307026,and 52477022)the National Key Research and Development Program of China(Grant No.2022YFE03150200)Shanghai Science and Technology Innovation Program(Grant No.23511101600)。
文摘This study investigates the effect of BaHfO_(3)(BHO)addition on the optical properties of YBa_2Cu_(3)O_(7-δ)(YBCO)superconducting thin films using spectroscopic ellipsometry.Through Raman spectroscopy and SEM analysis,optimal 10-min Ar ion etching effectively removes surface a-axis-oriented grains and Ba–Cu–O impurities,enhancing surface quality.Optical conductivity analysis reveals a doping-dependent evolution:10%BHO doping maximizes free carrier density and interband transition efficiency,attributed to optimized Cu–O bond contraction and reduced lattice distortions.Higher doping induces defect clustering,carrier scattering,and redshifted transitions due to lattice expansion.Dielectric function and loss function analyses confirm enhanced plasmonic behavior and flux pinning at 10%doping,while excessive doping degrades electronic transitions.These results highlight the critical role of controlled BHO addition and surface treatment in tailoring the optical and superconducting properties of YBCO,offering insights into the interplay among doping,carrier dynamics,and electronic structure in high-temperature superconductors(HTS).
基金supported by the National Natural Science Foundation of China(Grant Nos.22372142,12304028,12404027)the Foreign Expert Introduction Program(Grant No.G2023003004L)+6 种基金the Central Guiding Local Science and Technology Development Fund Projects(Grant No.236Z7605G)the Natural Science Foundation of Hebei Province(Grant Nos.B2024203051,A2024203023,A2024203002)the Science and Technology Project of Hebei Education Department(Grant No.JZX2023020)the Innovation Capability Improvement Project of Hebei Province(Grant No.22567605H)the Hebei Province Yan Zhao Huang Jin Tai Talent Program(Postdoctoral Platform,Grant No.B2024003003)the financial support from the Spanish Ministry of Science and Innovation(Grant No.PID2022139230NB-I00)the Department of Education,Universities and Research of the Basque Government and the University of the Basque Country(Grant No.IT1707-22)。
文摘Superconductivity in two-dimensional(2D)materials has attracted considerable attention due to their unique physical properties and potential for high-temperature operation.Boron-based 2D compounds are particularly promising,thanks to their structural flexibility and the emergence of strong electron-phonon coupling(EPC)associated with light elements.While most previous studies have focused on stabilizing boron sheets through metal incorporation,we propose an alternative approach based on multicenter bonding enabled by group-IV non-metallic elements(Si,Ge,Sn).The resulting XB_(2)(X=Si,Ge,Sn)monolayers,which adopt a MgB_(2)-like monolayer configuration,are stabilized by a seven-center two-electron(7c-2e)bonding network between the X atoms and the boron honeycomb lattice.This bonding lowers the energy of the B-p_(z)orbitals and enhances lattice stability.The superconducting transition temperature(T_(c))increases significantly with the atomic number of X—from 4.7 K in SiB_(2)to 13.3 K in GeB_(2)and 24.9 K in SnB_(2)—driven by an increased carrier density near the Fermi level(E_(F))and softening of the high-frequency E_(2)phonon mode.Furthermore,we design a SnB_4 monolayer,in which a Sn layer is sandwiched between the two boron layers.This structure enriches in-plane phonon modes and strengthens EPC,yielding a T_(c)of 38 K,close to the McMillan limit.These findings highlight the critical role of multicenter bonding and targeted phonon engineering in enabling high-T_(c)2D boron-based superconductors.
基金supported by the National Natural Science Foundation of China (Grant Nos.12074213 and 11574108)the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No.ZR2021ZD01)the Natural Science Foundation of Shandong Province (Grant No.ZR2023MA082)。
文摘In recent years,the research on superconductivity in one-dimensional(1D)materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices.However,the critical temperature(T_(c))of 1D superconductors is low.In this work,we theoretically investigate the possible high T_(c) superconductivity of(5,5)carbon nanotube(CNT).The pristine(5,5)CNT is a Dirac semimetal and can be modulated into a semiconductor by full hydrogenation.Interestingly,by further hole doping,it can be regulated into a metallic state with the sp^(3)-hybridized σ electrons metalized,and a giant Kohn anomaly appears in the optical phonons.The two factors together enhance the electron–phonon coupling,and lead to high-T_(c) superconductivity.When the hole doping concentration of hydrogenated-(5,5)CNT is 2.5 hole/cell,the calculated T_(c) is 82.3 K,exceeding the boiling point of liquid nitrogen.Therefore,the predicted hole-doped hydrogenated-(5,5)CNT provides a new platform for 1D high-T_(c) superconductivity and may have potential applications in 1D nanodevices.
基金supported by the National Key R&D Program of China (Grant Nos.2022YFA1403103 and 2019YFA0308603)the National Natural Science Foundation of China (Grant No.12304167)the Shandong Provincial Natural Science Foundation of China (Grant No.ZR2023QA020)。
文摘Interfacial superconductivity(IS)has been a topic of intense interest in condensed matter physics,due to its unique properties and exotic photoelectrical performance.However,there are few reports about IS systems consisting of two insulators.Here,motivated by the emergence of an insulator-metal transition in type-Ⅲ heterostructures and the superconductivity in some“special”two-dimensional(2D)semiconductors via electron doping,we predict that the 2D heterostructure SnSe_(2)/PtTe_(2) is a model system for realizing IS by using firstprinciples calculations.Our results show that due to slight but crucial interlayer charge transfer,SnSe_(2)/PtTe_(2) turns to be a type-Ⅲ heterostructure with metallic properties and shows a superconducting transition with the critical temperature(T_(c))of 3.73 K.Similar to the enhanced electron–phonon coupling(EPC)in the electrondoped SnSe_(2) monolayer,the IS in the SnSe_(2)/PtTe_(2) heterostructure mainly originates from the metallized SnSe_(2) layer.Furthermore,we find that its superconductivity is sensitive to tensile lattice strain,forming a domeshaped superconducting phase diagram.Remarkably,at 7%biaxial tensile strain,the superconducting T_(c) can increase more than twofold(8.80 K),resulting from softened acoustic phonons at the𝑀point and enhanced EPC strength.Our study provides a concrete example for realizing IS in type-Ⅲ heterostructures,which waits for future experimental verification.
基金supported by the National Key Research and Development Program of China (Grant Nos.2023YFA1406200 and 2022YFA-1405500)the National Natural Science Foundation of China (Grant Nos.12304021 and 52072188)+3 种基金Zhejiang Provincial Natural Science Foundation of China (Grant Nos.LQ23A040004 and MS26A040028)Natural Science Foundation of Ningbo (Grant Nos.2022J091 and ZX2025001430)the Program for Science and Technology Innovation Team in Zhejiang (Grant No.2021R01004)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT_15R23)。
文摘High-pressure electrides,characterized by the presence of interstitial quasi-atoms(ISQs),possess unique electronic structures and physical properties,such as diverse dimensions of electride states exhibiting different superconductivity,which has attracted significant attention.Here,we report a new electron-deficient type of electride Li_(4)Al and identify its phase transition progress with pressurization,where the internal driving force behind phase transitions,bonding characteristics,and superconducting behaviors have been revealed based on first-principles density functional theory.Through analysis of the bonding properties of electride Li_(4)Al,we demonstrate that the ISQs exhibiting increasingly covalent characteristics between Al ions play a critical role in driving the phase transition.Our electron–phonon coupling calculations indicate that all phases exhibit superconducting behaviors.Importantly,we prove that the ISQs behave as free electrons and demonstrate that the factor governing T_(c) is primarily derived from Li-p-hybridized electronic states with ISQ compositions.These electronic states are scattered by low-frequency phonons arising from mixed vibrations of Li and Al affected by ISQs to enhance electron–phonon coupling.Our study largely expands the research scope of electrides,provides new insight for understanding phase transitions,and elucidates the effects of ISQs on superconducting behavior.
基金supported by the National Key Research and Development of China(Grant Nos.2024YFA1408104 and 2021YFA1400400)the National Natural Science Foundation of China(Grant Nos.12374137,12434005,12074175,92165205,12004191,and 12550405)the Natural Science Foundation of Jiangsu Province(Grant No.BK20233001)。
文摘Motivated by the recent discovery of superconductivity in the kagome metal CsCr_(3)Sb_(5) under pressure,we theoretically investigate the superconducting pairing symmetry and the impact of spin–orbit coupling(SOC)in this system.By employing an effective four-orbital tight-binding model and solving the linearized gap equation within the random phase approximation,we find that the large inter-orbital spin fluctuations enhanced by Hund’s coupling promote a superconducting gap function with E_(2g)symmetry.The inclusion of SOC further stabilizes this gap symmetry.Our analysis also reveals that the d_(x^(2)-y^(2))orbital plays the dominant role in forming the superconducting pairs.
基金supported by the National Key R&D Program of China (Grant No.2022YFA1403201)the National Natural Science Foundation of China (Grant Nos.12125404,T2495231,123B2049,and 12204138)+9 种基金the Advanced MaterialsNational Science and Technology Major Project (Grant No.2024ZD0607000)the Natural Science Foundation of Jiangsu Province (Grant Nos.BK20233001 and BK20253009)the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant No.2024ZB002)the China Postdoctoral Science Foundation (Grant No.2025M773331)the Fundamental and Interdisciplinary Disciplines Breakthrough Plan of the Ministry of Education of Chinathe AI&AI for Science program of Nanjing UniversityArtificial Intelligence and Quantum physics (AIQ) program of Nanjing Universitythe Fundamental Research Funds for the Central Universitiesthe Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant Nos.NY224165,NY220038,and NY219087)the Hua Li Talents Program of Nanjing University of Posts and Telecommunications。
文摘We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X represents transition metal elements.Systematic analysis of electronic band structures,phonon dispersions,and electron-phonon coupling reveals that substitution of MA binary metal combinations and X metal atoms can create favorable conditions for superconductivity.Mapping of superconducting critical temperatures,combined with dynamical stability analysis through phonon calculations,identifies ten superconducting candidates at ambient pressure.Among these,LiNaAgH_(6) exhibits nearly-free-electron behavior reminiscent of monovalent electron superconductors.It demonstrates exceptional superconducting properties with electron–phonon coupling λ=2.707,which yields a superconducting transition temperature T_(c) of 206.4 K using the Allen–Dynes formula.Its structural analogs MgNaPdH_(6),LiMgPdH_(6),LiMgAgH_(6),LiMgAuH_(6) all exhibit superconducting transition temperatures above 110 K.These findings advance our fundamental understanding of superconductivity in quaternary hydrides and provide guidance for rational design of new high-temperature superconducting materials.
文摘Applied field magnetoplasmadynamic thrusters(AF-MPDTs), with their high specific impulse and considerable thrust, are increasingly favored for large-scale space missions. This paper presents the composition, functionality, and testing methods of a high-power electric propulsion performance testing system, along with the vacuum ignition test results of a 100 kW superconducting MPD thruster. The relationships between thruster efficiency, magnetic field strength, current,and mass flow rate are analyzed. For each combination of current and flow rate in an AF-MPDT, there is an optimal magnetic field strength where the thruster efficiency reaches its peak. Under conditions of 320 A current and 60 mg/s flow rate,the optimal magnetic field strength is 0.5 T, yielding the highest thruster efficiency of 71%.
基金the Innovation Program for Quantum Science and Technology(Grant No.2023ZD0300100)the National Key Research and Development Program of China(Grant Nos.2023YFB3809600 and 2023YFC3007801)+1 种基金the National Natural Science Foundation of China(Grant Nos.62301543 and U24A20320)the Shanghai Sailing Program(Grant No.21YF1455700).
文摘Conventional superconducting nanowire single-photon detectors(SNSPDs)have been typically limited in their applications due to their size,weight,and power consumption,which confine their use to laboratory settings.However,with the rapid development of remote imaging,sensing technologies,and long-range quantum communication with fewer topographical constraints,the demand for high-efficiency single-photon detectors integrated with avionic platforms is rapidly growing.We herein designed and manufactured the first drone-based SNSPD system with a system detection efficiency(SDE)as high as 91.8%.This drone-based system incorporates high-performance NbTiN SNSPDs,a self-developed miniature liquid helium dewar,and custom-built integrated electrical setups,making it capable of being launched in complex topographical conditions.Such a drone-based SNSPD system may open the use of SNSPDs for applications that demand high SDE in complex environments.
文摘In the 9 December 2024 issue of Nature[1],a team of Google engineers reported breakthrough results using“Willow”,their lat-est quantum computing chip(Fig.1).By meeting a milestone“below threshold”reduction in the rate of errors that plague super-conducting circuit-based quantum computing systems(Fig.2),the work moves the field another step towards its promised super-charged applications,albeit likely still many years away.Areas expected to benefit from quantum computing include,among others,drug discovery,materials science,finance,cybersecurity,and machine learning.
基金supported by the National Natural Science Foundation of China(12072136).
文摘Research on the mechanical–electrical properties is crucial for designing and preparing high-temperature superconducting(HTS)cables.Various winding core structures can influence the mechanical–electrical behavior of cables,but the impact of alterations in the winding core structure on the mechanical–electrical behavior of superconducting cables remains unclear.This paper presents a 3D finite element model to predict the performance of three cables with different core structures when subjected to transverse compression and axial tension.The three cables analyzed are CORC(conductor-on-round-core),CORT(conductor-on-round-tube),and HFRC(conductor-on-spiral-tube).A parametric analysis is carried out by varying the core diameter and inner-to-outer diameter ratio.Results indicate that the CORT cable demonstrates better performance in transverse compression compared to the CORC cable,aligning with experimental data.Among the three cables,the HFRC cables exhibit the weakest resistance to transverse deformation.However,the HFRC cable demonstrates superior tensile deformation resistance compared to the CORT cable,provided that the transverse compression properties are maintained.Finite element results also show that the optimum inner-to-outer diameter ratios for achieving the best transverse compression performance are approximately 0.8 for CORT cables and 0.6 for HFRC cables.Meanwhile,the study explores the effect of structural changes in HTS cable winding cores on their electromagnetic properties.It recommends utilizing small tape gaps,lower frequencies,and spiral core construction to minimize eddy losses.The findings presented in this paper offer valuable insights for the commercialization and practical manufacturing of HTS cables.
基金supported by the studies of intelligent LLRF control algorithms for superconducting RF cavities(No.E129851YR0)the National Natural Science Foundation of China(No.U22A20261)Applications of Artificial Intelligence in the Stability Study of Superconducting Linear Accelerators(No.E429851YR0)。
文摘Superconducting radio-frequency(SRF)cavities are the core components of SRF linear accelerators,making their stable operation considerably important.However,the operational experience from different accelerator laboratories has revealed that SRF faults are the leading cause of short machine downtime trips.When a cavity fault occurs,system experts analyze the time-series data recorded by low-level RF systems and identify the fault type.However,this requires expertise and intuition,posing a major challenge for control-room operators.Here,we propose an expert feature-based machine learning model for automating SRF cavity fault recognition.The main challenge in converting the"expert reasoning"process for SRF faults into a"model inference"process lies in feature extraction,which is attributed to the associated multidimensional and complex time-series waveforms.Existing autoregression-based feature-extraction methods require the signal to be stable and autocorrelated,resulting in difficulty in capturing the abrupt features that exist in several SRF failure patterns.To address these issues,we introduce expertise into the classification model through reasonable feature engineering.We demonstrate the feasibility of this method using the SRF cavity of the China accelerator facility for superheavy elements(CAFE2).Although specific faults in SRF cavities may vary across different accelerators,similarities exist in the RF signals.Therefore,this study provides valuable guidance for fault analysis of the entire SRF community.
基金supported by the National Nature Science Foundation of China(Grant No.52302507)。
文摘The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry and can significantly enhance the energy efficiency of aircraft propulsion system.Electric motor is the most critical electromechanical energy conversion component in an aircraft electric propulsion system(EPS).High-performance electric motors,power electronic converters and EPS control form the foundation of the EPA.This paper provides an overview of the characteristics of electric motors for EPA,analyzes the inverter topologies of EPSs,and reviews ongoing EPA projects.The article highlights the latest advancements in three types of motors:superconducting motors(SCMs),permanent magnet synchronous motors(PMSMs),and induction motors(IMs).It summarizes the control system architectures of current EPA initiatives and,building on this foundation,proposes future research directions for EPSs.These include cutting-edge areas such as high-performance motors and advanced manufacturing technologies,Ga N-or Si C-based inverter integration and innovation,electric propulsion control systems,and optimization of wiring systems.
基金supported by the Large Research Infrastructures China initiative Accelerator Driven System(No.2017-000052-75-01-000590)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022422)+1 种基金the Young Scientists of National Natural Science Foundation of China(No.12005275)the Advanced Energy Science and Technology Guangdong Laboratory(No.HND22PTZZYY)。
文摘Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.
