Due to the interconnection of various renewable energies and adaptive technologies, voltage quality and frequency stability of modern power systems are becoming erratic. Superconducting magnetic energy storage(SMES),f...Due to the interconnection of various renewable energies and adaptive technologies, voltage quality and frequency stability of modern power systems are becoming erratic. Superconducting magnetic energy storage(SMES),for its dynamic characteristic, is very efficient for rapid exchange of electrical power with grid during small and large disturbances to address those instabilities.In addition,SMES plays an important role in integrating renewable sources such as wind generators to power grid by controlling output power of wind plant and improving the stability of power system.Efficient application of SMES in various power system operations depends on the proper location in the power system, exact energy and power ratings and appropriate controllers. In this paper, an effort is given to explain SMES device and its controllability to mitigate the stability of power grid integrated with wind power generation systems.展开更多
We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screenin...We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.展开更多
The magnetocaloric effect （MCE） in many rare earth （RE） based intermetallic compounds has been extensively in- vestigated during the last two decades, not only due to their potential applications for magnetic refr...The magnetocaloric effect （MCE） in many rare earth （RE） based intermetallic compounds has been extensively in- vestigated during the last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress on studying the magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal（s） （Zn, Mg, and Cd）. Some of them exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented.展开更多
The binary polyhydrides of heavy rare earth lutetium that shares a similar valence electron configuration to lanthanum have been experimentally discovered to be superconductive.The lutetium polyhydrides were successfu...The binary polyhydrides of heavy rare earth lutetium that shares a similar valence electron configuration to lanthanum have been experimentally discovered to be superconductive.The lutetium polyhydrides were successfully synthesized at high pressure and high temperature conditions using a diamond anvil cell in combinations with the in-situ high pressure laser heating technique.The resistance measurements as a function of temperature were performed at the same pressure of synthesis in order to study the transitions of superconductivity(SC).The superconducting transition with a maximum onset temperature(Tc)71 K was observed at pressure of 218 GPa in the experiments.The Tcdecreased to 65 K when pressure was at 181 GPa.From the evolution of SC at applied magnetic fields,the upper critical field at zero temperatureμ0Hc2(0)was obtained to be~36 T.The in-situ high pressure X-ray diffraction experiments imply that the high TcSC should arise from the Lu4H23phase with Pm3n symmetry that forms a new type of hydrogen cage framework different from those reported for previous light rare earth polyhydride superconductors.展开更多
We present a review of terahertz plasmonic metamaterial devices that have functionalities and applications ranging from sensing, enhanced electromagnetic fields, and near field manipulation. Metamaterials allow the pr...We present a review of terahertz plasmonic metamaterial devices that have functionalities and applications ranging from sensing, enhanced electromagnetic fields, and near field manipulation. Metamaterials allow the properties of light propagation to be manipulated at will by using a combination of appropriately designed geometry and suitable materials at the unit cell level. In this review, we first discuss the sensing aspect of a planar plasmonic metamaterial and how to overcome its limitations. Conventional symmetric metamaterials are limited by their low Q factor, thus we probed the symmetry broken plasmonic metama- terial structures in which the interference between a broad continuum mode and a narrow localized mode leads to the excitation of the sharp Fano resonances. We also discuss the near field mediated excitation of dark plasmonic modes in metamaterials that is caused by a strong coupling from the bright mode res- onator. The near field coupling between the dark and bright mode resonances leads to classical analogue of electromagnetically induced transparency in plasmonic systems. Finally, we discuss active switching in terahertz metamateriMs based on high temperature superconductors that holds the promise of reducing the resistive losses in these systems, though it fails to suppress the radiation loss in plasmonic metamaterial at terahertz frequencies.展开更多
Based on the assumption that the superconducting state belongs to a single irreducible representation of lattice symmetry, we propose that the pairing symmetry in all measured iron-based superconductors is generally c...Based on the assumption that the superconducting state belongs to a single irreducible representation of lattice symmetry, we propose that the pairing symmetry in all measured iron-based superconductors is generally consistent with the A1g s-wave. Robust s-wave pairing throughout the different families of iron-based superconductors at different doping regions signals two fundamental principles behind high-To superconducting mechanisms： （i） the correspondence principle： the short-range magnetic-exchange interactions and the Fermi surfaces act collaboratively to achieve high-Tc superconductivity and determine pairing symmetries; （ii） the magnetic-selection pairing rule： supercon- ductivity is only induced by the magnetic-exchange couplings from the super-exchange mechanism through cation-anion-cation chemical bonding. These principles explain why unconventional high- Tc superconductivity appears to be such a rare but robust phenomena, with its strict requirements regarding the electronic environment. The results will help us to identify new electronic structures that can support high-Tc superconductivity.展开更多
We have investigated the phase equilibria in (RE)BaCuO/Ag systems, the influence of Ag on the processing of (RE)BaCuO/Ag composites and the resulting properties. YBaCuO/Ag composites have been grown by the modified me...We have investigated the phase equilibria in (RE)BaCuO/Ag systems, the influence of Ag on the processing of (RE)BaCuO/Ag composites and the resulting properties. YBaCuO/Ag composites have been grown by the modified melt crystallization process with YBa2Cu3O7, Y2O3, Pt and Ag2O in the precursor. The improved strength of the YBaCuO/Ag composites compared with the conventional YBaCuO bulk material permitted us to magnetize these materials to achieve trapped fields up to 16 T (at 24 K) in the gap of a mini-magnet. The investigation of the microstructure revealed a remarkable increase of the spacing between micro-cracks especially of those perpendicular to a/b-planes when 12wt%Ag was added. In the case of SmBaCuO/Ag composites, Ag has a strong influence on processing and causes interactions between RE123 seeds and the sample. We show the growth of single-grain SmBaCuO/Ag composites in air and discuss the influence of post-annealing on increasing Tc and Jc. Furthermore, YBaCuO/Ag composites have been shown to be appropriate materials used as a solder to join large single grains to large arrays or to 'repair' grain boundaries in arrays grown by a multiseeding technique.展开更多
A dream long held by physicists has been to raise the critical temperature(Tc)—the temperature below which the material exhibits no electrical resistance—of a superconductor to room temperature.The most recent excit...A dream long held by physicists has been to raise the critical temperature(Tc)—the temperature below which the material exhibits no electrical resistance—of a superconductor to room temperature.The most recent excitement in that regard has centered on rare-earth superhydrides,of which LaH10 at 190 GPa has a remarkably high Tc of 260 K.展开更多
Chemical substitution during growth is a well-established method to manipulate electronic states of quantum materials, and leads to rich spectra of phase diagrams in cuprate and iron-based superconductors. Here we rep...Chemical substitution during growth is a well-established method to manipulate electronic states of quantum materials, and leads to rich spectra of phase diagrams in cuprate and iron-based superconductors. Here we report a novel and generic strategy to achieve nonvolatile electron doping in series of(i.e.11 and 122 structures) Fe-based superconductors by ionic liquid gating induced protonation at room temperature. Accumulation of protons in bulk compounds induces superconductivity in the parent compounds, and enhances the Tclargely in some superconducting ones. Furthermore, the existence of proton in the lattice enables the first proton nuclear magnetic resonance(NMR) study to probe directly superconductivity. Using Fe S as a model system, our NMR study reveals an emergent high-Tcphase with no coherence peak which is hard to measure by NMR with other isotopes. This novel electric-fieldinduced proton evolution opens up an avenue for manipulation of competing electronic states(e.g.Mott insulators), and may provide an innovative way for a broad perspective of NMR measurements with greatly enhanced detecting resolution.展开更多
What factors fundamentally determine the value of superconducting transition temperature Tc in high temperature superconductors has been the subject of intense debate.Following the establishment of an empirical law kn...What factors fundamentally determine the value of superconducting transition temperature Tc in high temperature superconductors has been the subject of intense debate.Following the establishment of an empirical law known as Homes'law,there is a growing consensus in the community that the Tc value of the cuprate superconductors is closely linked to the superfluid density(ρ_(s))of its ground state and the conductivity(σ)of its normal state.However,all the data supporting this empirical law(ρ_(s)=AσT_(c))have been obtained from the ambientpressure superconductors.In this study,we present the first high-pressure results about the connection of the quantities of ρ_(s) and σ with T_(c),through the studies on the Bi_(1.74)Pb_(0.38)Sr_(1.88)CuO_(6+δ)and Bi_(2)Sr_(2)CaCu_(2)O_(8+δ),in which the value of their high-pressure resistivity(ρ=1/σ)is achieved by adopting our newly established method,while the quantity ofρs is extracted using Homes'law.We highlight that the Tc values are strongly linked to the joint response factors of magnetic field and electric field,i.e.,ρ_(s) and σ,respectively,implying that the physics determining T_(c) is governed by the intrinsic electromagnetic fields of the system.展开更多
The discovery of EuFeAs_(2),currently the only charge-neutral parent phase of the 112-type iron-pnictide system,provides a new platform for the study of elemental doping effects on magnetism and superconductivity(SC)....The discovery of EuFeAs_(2),currently the only charge-neutral parent phase of the 112-type iron-pnictide system,provides a new platform for the study of elemental doping effects on magnetism and superconductivity(SC).In this study,a series of polycrystalline EuFe_(1-y)Co_(y)As_(2)and Eu_(0.9)Pr_(0.1)Fe_(1-y)Co_(y)As_(2)samples are synthesized through solid-state reaction,and the evolutions of SC and magnetism with Co doping in EuFeAs_(2)and Eu_(0.9)Pr_(0.1)FeAs_(2)are investigated by electrical transport and magnetic susceptibility measurements.For EuFe_(1-y)Co_(y)As_(2),the Eu-related antiferromagnetic(AFM)transition around 40 K is barely affected by Co doping,while the Fe-related spin density wave(SDW)transition temperature drops rapidly.Meanwhile,SC is induced by a trace amount of Co doping,with a highest transition temperature T_(c)~28 K found in EuFe0.9Co0.1As_(2).For the Eu_(0.9)Pr_(0.1)Fe1-yCo_(y)As_(2)series,the magnetism and superconductivity show similar evolutions upon Co doping,and the highest T_(c)is enhanced to 30.6 K with an optimum doping level y~0.07.Our results shed light on the competition between SC and SDW with Co doping in the 112-type EuFeAs_(2)system.展开更多
The Boltzmann local physical kinetics forecasts the destruction of SC regime because of the heat movement of particles. Then, the most fundamental distinction between a strange metal and a conventional metal is the ab...The Boltzmann local physical kinetics forecasts the destruction of SC regime because of the heat movement of particles. Then, the most fundamental distinction between a strange metal and a conventional metal is the absence of well-defined quasi-particles. Here, we show that the mentioned “quasi-particles” are solitons, which are formed as a result of self-organization of ionized matter. Shortcomings of the Boltzmann physical kinetics consist in the local description of the transport processes on the level of infinitely small physical volumes as elements of diagnostics. The non-local physics leads to the theory superconductivity including the high temperature diapason. The generalized non-local non-stationary London’s formula is derived.展开更多
Van Hove singularities in proximity to the Fermi level promote electronic interactions and generate diverse competing instabilities.It is also known that a nontrivial Berry phase derived from spin–orbit coupling can ...Van Hove singularities in proximity to the Fermi level promote electronic interactions and generate diverse competing instabilities.It is also known that a nontrivial Berry phase derived from spin–orbit coupling can introduce an intriguing decoration into the interactions and thus alter correlated phenomena.However,it is unclear how and what type of new physics can emerge in a system featured by the interplay between van Hove singularities(VHSs)and the Berry phase.Here,based on a general Rashba model on the square lattice,we comprehensively explore such an interplay and its significant influence on the competing electronic instabilities by performing a parquet renormalization group analysis.Despite the existence of a variety of comparable fluctuations in the particle–particle and particle-hole channels associated with higher-order VHSs,we find that the chiral p±ip pairings emerge as two stable fixed trajectories within the generic interaction parameter space,namely the system becomes a robust topological superconductor.The chiral pairings stem from the hopping interaction induced by the nontrivial Berry phase.The possible experimental realization and implications are discussed.Our work sheds new light on the correlated states in quantum materials with strong spin–orbit coupling(SOC)and offers fresh insights into the exploration of topological superconductivity.展开更多
We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of t...We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te.However,the band gap between the electron-and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange,which drive the system to a nontrivial topological state predicted by theoretical calculations.Our results provide a clear experimental indication that the FeTe_(1-x)Se_x monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.展开更多
The infinite-layer cuprate ACu O_(2)(A=Ca,Sr,Ba)possesses the simplest crystal structure among numerous cuprate superconductors and can serve as a prototypical system to explore the unconventional superconductivity.Ba...The infinite-layer cuprate ACu O_(2)(A=Ca,Sr,Ba)possesses the simplest crystal structure among numerous cuprate superconductors and can serve as a prototypical system to explore the unconventional superconductivity.Based on the first-principles electronic structure calculations,we have studied the electronic and magnetic properties of the infinite-layer cuprate SrCuO_(2)from a phonon perspective.We find that interesting fluctuations of charges,electrical dipoles,and local magnetic moments can be induced by the atomic displacements of phonon modes in SrCuO_(2)upon the hole doping.Among all optical phonon modes of SrCuO_(2)in the antiferromagnetic Néel state,only the A_(1g)mode that involves the full-breathing O vibrations along the Cu-O bonds can cause significant fluctuations of local magnetic moments on O atoms and dramatic charge redistributions between Cu and O atoms.Notably,due to the atomic displacements of the A_(1g)mode,both the charge fluctuations on Cu and the electrical dipoles on O show a dome-like evolution with increasing hole doping,quite similar to the experimentally observed behavior of the superconducting T_(c);in comparison,the fluctuations of local magnetic moments on O display a monotonic enhancement along with the hole doping.Further analyses indicate that around the optimal doping,there exists a large softening in the frequency of the A_(1g)phonon mode and a van Hove singularity in the electronic structure close to the Fermi level,suggesting potential electron-phonon coupling.Our work reveals the important role of the full-breathing O phonon mode playing in the infinite-layer SrCuO_(2),which may provide new insights in understanding the cuprate superconductivity.展开更多
We construct a three-dimensional topological superconductor Bogoliubov–de Gennes(BdG)Hamiltonian with the normal state being a three-dimensional topological insulator.By introducing inter-orbital spin-triplet pairing...We construct a three-dimensional topological superconductor Bogoliubov–de Gennes(BdG)Hamiltonian with the normal state being a three-dimensional topological insulator.By introducing inter-orbital spin-triplet pairings term△3,there are topological Majorana nodes in the bulk and they are connected by Majorana Fermi arcs on the surface,similar to the case of Weyl semimetal.Furthermore,by adding an inversion-breaking term to the normal state,momentum-independent pairing terms with different parities can coexist in the Bd G Hamiltonian,which creates more Majorana modes similar to Andreev bound states and a richer phase diagram.展开更多
The remarkable electromagnetic characteristics inherent in unconventional superconductors have catalyzed the advance-ment of numerous technological innovations,spanning from energy-efficient power transmission and hig...The remarkable electromagnetic characteristics inherent in unconventional superconductors have catalyzed the advance-ment of numerous technological innovations,spanning from energy-efficient power transmission and high-field magnets to sensitive detectors and quantum computing systems.Central to the functionality of these applications lies the superconducting characteristics,which govern pivotal phenomena including Cooper pair formation and macroscopic phase coherence,resulting in the attainment of zero electrical resistance,complete diamagnetism,and the Josephson tunneling effect.The complex phases and orders in these ma-terials significantly alter their key electronic and magnetic properties,posing challenges in elucidating the underlying physics and further enhancing their functional capabilities.The multiscale approach,representing a useful strategy for understanding materials across diverse length scales using a variety of experimental tools,can reveal intricate details in real and reciprocal spaces,facilitating cross-validation.In this brief review,we introduce the principle of the multiscale approach along with examples demonstrating its efficacy in unraveling the electronic and magnetic properties of unconventional superconductors.展开更多
文摘Due to the interconnection of various renewable energies and adaptive technologies, voltage quality and frequency stability of modern power systems are becoming erratic. Superconducting magnetic energy storage(SMES),for its dynamic characteristic, is very efficient for rapid exchange of electrical power with grid during small and large disturbances to address those instabilities.In addition,SMES plays an important role in integrating renewable sources such as wind generators to power grid by controlling output power of wind plant and improving the stability of power system.Efficient application of SMES in various power system operations depends on the proper location in the power system, exact energy and power ratings and appropriate controllers. In this paper, an effort is given to explain SMES device and its controllability to mitigate the stability of power grid integrated with wind power generation systems.
基金supported by the National Natural Science Foundation and Ministry of Science and Technology of China(2015CB921000 and 2012CB921402)Yihua Wang is partially supported by the Urbanek Fellowship of the Department of Applied Physics at Stanford UniversityK.A.Moler is supported by the Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division,under Contract DEAC02-76SF00515
文摘We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374081 and 11004044)the Fundamental Research Funds for the Central Universities+4 种基金China(Grant Nos.N150905001L1509006and N140901001)the Japan Society for the Promotion of Science Postdoctoral Fellowships for Foreign Researchers(Grant No.P10060)the Alexander von Humboldt(Av H)Foundation(Research stipend to L.Li)
文摘The magnetocaloric effect （MCE） in many rare earth （RE） based intermetallic compounds has been extensively in- vestigated during the last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress on studying the magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal（s） （Zn, Mg, and Cd）. Some of them exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented.
基金supported by the Natural Science Foundation of Chinathe National Key R&D Program of ChinaChinese Academy of Sciences through research projects(Grant Nos.2018YFA0305700,2021YFA1401-800,and XDB33010200)。
文摘The binary polyhydrides of heavy rare earth lutetium that shares a similar valence electron configuration to lanthanum have been experimentally discovered to be superconductive.The lutetium polyhydrides were successfully synthesized at high pressure and high temperature conditions using a diamond anvil cell in combinations with the in-situ high pressure laser heating technique.The resistance measurements as a function of temperature were performed at the same pressure of synthesis in order to study the transitions of superconductivity(SC).The superconducting transition with a maximum onset temperature(Tc)71 K was observed at pressure of 218 GPa in the experiments.The Tcdecreased to 65 K when pressure was at 181 GPa.From the evolution of SC at applied magnetic fields,the upper critical field at zero temperatureμ0Hc2(0)was obtained to be~36 T.The in-situ high pressure X-ray diffraction experiments imply that the high TcSC should arise from the Lu4H23phase with Pm3n symmetry that forms a new type of hydrogen cage framework different from those reported for previous light rare earth polyhydride superconductors.
基金partially supported by the US National Science Foundation
文摘We present a review of terahertz plasmonic metamaterial devices that have functionalities and applications ranging from sensing, enhanced electromagnetic fields, and near field manipulation. Metamaterials allow the properties of light propagation to be manipulated at will by using a combination of appropriately designed geometry and suitable materials at the unit cell level. In this review, we first discuss the sensing aspect of a planar plasmonic metamaterial and how to overcome its limitations. Conventional symmetric metamaterials are limited by their low Q factor, thus we probed the symmetry broken plasmonic metama- terial structures in which the interference between a broad continuum mode and a narrow localized mode leads to the excitation of the sharp Fano resonances. We also discuss the near field mediated excitation of dark plasmonic modes in metamaterials that is caused by a strong coupling from the bright mode res- onator. The near field coupling between the dark and bright mode resonances leads to classical analogue of electromagnetically induced transparency in plasmonic systems. Finally, we discuss active switching in terahertz metamateriMs based on high temperature superconductors that holds the promise of reducing the resistive losses in these systems, though it fails to suppress the radiation loss in plasmonic metamaterial at terahertz frequencies.
基金Acknowledgements The work was supported by the National Basic Reseaxch Program of China, the National Natural Science Foundation of China （NSFC）, and the Strategic Priority Research Program of the Chinese Academy of Sciences.
文摘Based on the assumption that the superconducting state belongs to a single irreducible representation of lattice symmetry, we propose that the pairing symmetry in all measured iron-based superconductors is generally consistent with the A1g s-wave. Robust s-wave pairing throughout the different families of iron-based superconductors at different doping regions signals two fundamental principles behind high-To superconducting mechanisms： （i） the correspondence principle： the short-range magnetic-exchange interactions and the Fermi surfaces act collaboratively to achieve high-Tc superconductivity and determine pairing symmetries; （ii） the magnetic-selection pairing rule： supercon- ductivity is only induced by the magnetic-exchange couplings from the super-exchange mechanism through cation-anion-cation chemical bonding. These principles explain why unconventional high- Tc superconductivity appears to be such a rare but robust phenomena, with its strict requirements regarding the electronic environment. The results will help us to identify new electronic structures that can support high-Tc superconductivity.
基金Supported by Bundesminister fur Bildung,Forschung,Wissenschaft und Technologie(BMBF,13N7677)Sachsischer Minister fur Wissenschaft und Kunst and VEGA,Slovak Academy of Science
文摘We have investigated the phase equilibria in (RE)BaCuO/Ag systems, the influence of Ag on the processing of (RE)BaCuO/Ag composites and the resulting properties. YBaCuO/Ag composites have been grown by the modified melt crystallization process with YBa2Cu3O7, Y2O3, Pt and Ag2O in the precursor. The improved strength of the YBaCuO/Ag composites compared with the conventional YBaCuO bulk material permitted us to magnetize these materials to achieve trapped fields up to 16 T (at 24 K) in the gap of a mini-magnet. The investigation of the microstructure revealed a remarkable increase of the spacing between micro-cracks especially of those perpendicular to a/b-planes when 12wt%Ag was added. In the case of SmBaCuO/Ag composites, Ag has a strong influence on processing and causes interactions between RE123 seeds and the sample. We show the growth of single-grain SmBaCuO/Ag composites in air and discuss the influence of post-annealing on increasing Tc and Jc. Furthermore, YBaCuO/Ag composites have been shown to be appropriate materials used as a solder to join large single grains to large arrays or to 'repair' grain boundaries in arrays grown by a multiseeding technique.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11534003,11874175,11874176,12074138,and 11974134)the Science Challenge Project(Grant No.TZ2016001)+3 种基金the Fundamental Research Funds for the Central Universities(Jilin University,JLU)the Program for JLU Science and Technology Innovative Research Team(JLUSTIRT)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33000000)the Jilin Province Outstanding Young Talents Project(Grant No.20190103040JH).
文摘A dream long held by physicists has been to raise the critical temperature(Tc)—the temperature below which the material exhibits no electrical resistance—of a superconductor to room temperature.The most recent excitement in that regard has centered on rare-earth superhydrides,of which LaH10 at 190 GPa has a remarkably high Tc of 260 K.
基金supported by the Ministry of Science and Technology of China(2015CB921700,2016YFA0300504,2016YFA0301004,2016YFA0300401 and 2017YFA0302903)the National Natural Science Foundation of China(11374364,11522429,11374011 and 11534005)
文摘Chemical substitution during growth is a well-established method to manipulate electronic states of quantum materials, and leads to rich spectra of phase diagrams in cuprate and iron-based superconductors. Here we report a novel and generic strategy to achieve nonvolatile electron doping in series of(i.e.11 and 122 structures) Fe-based superconductors by ionic liquid gating induced protonation at room temperature. Accumulation of protons in bulk compounds induces superconductivity in the parent compounds, and enhances the Tclargely in some superconducting ones. Furthermore, the existence of proton in the lattice enables the first proton nuclear magnetic resonance(NMR) study to probe directly superconductivity. Using Fe S as a model system, our NMR study reveals an emergent high-Tcphase with no coherence peak which is hard to measure by NMR with other isotopes. This novel electric-fieldinduced proton evolution opens up an avenue for manipulation of competing electronic states(e.g.Mott insulators), and may provide an innovative way for a broad perspective of NMR measurements with greatly enhanced detecting resolution.
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1401800 and 2022YFA1403900)the National Natural Science Foundation of China(Grant Nos.U2032214,12122414,12104487,and 12004419)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)supported by the US Department of Energy,Office of Basic Energy Sciences(Grant No.DOE-sc0012704)。
文摘What factors fundamentally determine the value of superconducting transition temperature Tc in high temperature superconductors has been the subject of intense debate.Following the establishment of an empirical law known as Homes'law,there is a growing consensus in the community that the Tc value of the cuprate superconductors is closely linked to the superfluid density(ρ_(s))of its ground state and the conductivity(σ)of its normal state.However,all the data supporting this empirical law(ρ_(s)=AσT_(c))have been obtained from the ambientpressure superconductors.In this study,we present the first high-pressure results about the connection of the quantities of ρ_(s) and σ with T_(c),through the studies on the Bi_(1.74)Pb_(0.38)Sr_(1.88)CuO_(6+δ)and Bi_(2)Sr_(2)CaCu_(2)O_(8+δ),in which the value of their high-pressure resistivity(ρ=1/σ)is achieved by adopting our newly established method,while the quantity ofρs is extracted using Homes'law.We highlight that the Tc values are strongly linked to the joint response factors of magnetic field and electric field,i.e.,ρ_(s) and σ,respectively,implying that the physics determining T_(c) is governed by the intrinsic electromagnetic fields of the system.
基金supported by the National Natural Science Foundation of China(Grant No.11774402)the National Key Research Program of China(Grant Nos.2018YFA0704200,and 2016YFA0300301)。
文摘The discovery of EuFeAs_(2),currently the only charge-neutral parent phase of the 112-type iron-pnictide system,provides a new platform for the study of elemental doping effects on magnetism and superconductivity(SC).In this study,a series of polycrystalline EuFe_(1-y)Co_(y)As_(2)and Eu_(0.9)Pr_(0.1)Fe_(1-y)Co_(y)As_(2)samples are synthesized through solid-state reaction,and the evolutions of SC and magnetism with Co doping in EuFeAs_(2)and Eu_(0.9)Pr_(0.1)FeAs_(2)are investigated by electrical transport and magnetic susceptibility measurements.For EuFe_(1-y)Co_(y)As_(2),the Eu-related antiferromagnetic(AFM)transition around 40 K is barely affected by Co doping,while the Fe-related spin density wave(SDW)transition temperature drops rapidly.Meanwhile,SC is induced by a trace amount of Co doping,with a highest transition temperature T_(c)~28 K found in EuFe0.9Co0.1As_(2).For the Eu_(0.9)Pr_(0.1)Fe1-yCo_(y)As_(2)series,the magnetism and superconductivity show similar evolutions upon Co doping,and the highest T_(c)is enhanced to 30.6 K with an optimum doping level y~0.07.Our results shed light on the competition between SC and SDW with Co doping in the 112-type EuFeAs_(2)system.
文摘The Boltzmann local physical kinetics forecasts the destruction of SC regime because of the heat movement of particles. Then, the most fundamental distinction between a strange metal and a conventional metal is the absence of well-defined quasi-particles. Here, we show that the mentioned “quasi-particles” are solitons, which are formed as a result of self-organization of ionized matter. Shortcomings of the Boltzmann physical kinetics consist in the local description of the transport processes on the level of infinitely small physical volumes as elements of diagnostics. The non-local physics leads to the theory superconductivity including the high temperature diapason. The generalized non-local non-stationary London’s formula is derived.
基金supports by the Ministry of Science and Technology(2022YFA1403901)the National Natural Science Foundation of China(11920101005,11888101,and 12047503)+2 种基金the New Cornerstone Investigator Programpartially supported by Chinese Academy of Sciences under contract No.JZHKYPT-2021–08supports from China Postdoctoral Science Foundation Fellowship(2022M723112)。
文摘Van Hove singularities in proximity to the Fermi level promote electronic interactions and generate diverse competing instabilities.It is also known that a nontrivial Berry phase derived from spin–orbit coupling can introduce an intriguing decoration into the interactions and thus alter correlated phenomena.However,it is unclear how and what type of new physics can emerge in a system featured by the interplay between van Hove singularities(VHSs)and the Berry phase.Here,based on a general Rashba model on the square lattice,we comprehensively explore such an interplay and its significant influence on the competing electronic instabilities by performing a parquet renormalization group analysis.Despite the existence of a variety of comparable fluctuations in the particle–particle and particle-hole channels associated with higher-order VHSs,we find that the chiral p±ip pairings emerge as two stable fixed trajectories within the generic interaction parameter space,namely the system becomes a robust topological superconductor.The chiral pairings stem from the hopping interaction induced by the nontrivial Berry phase.The possible experimental realization and implications are discussed.Our work sheds new light on the correlated states in quantum materials with strong spin–orbit coupling(SOC)and offers fresh insights into the exploration of topological superconductivity.
基金supported by grants from the Ministry of Science and Technology of China(2015CB921000,2016YFA0401000,2015CB921301,2016YFA0300300)the National Natural Science Foundation of China(11574371,11274362,1190020,11334012,11274381,11674371)
文摘We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te.However,the band gap between the electron-and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange,which drive the system to a nontrivial topological state predicted by theoretical calculations.Our results provide a clear experimental indication that the FeTe_(1-x)Se_x monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1403103,and 2019YFA0308603)the Beijing Natural Science Foundation(Grant No.Z200005)+2 种基金the National Natural Science Foundation of China(Grant Nos.12174443,and 11934020)supported by the National Key R&D Program of China(Grant No.2017YFA0302903)supported by the Project funded by China Postdoctoral Science Foundation(Grant No.2022M723355)。
文摘The infinite-layer cuprate ACu O_(2)(A=Ca,Sr,Ba)possesses the simplest crystal structure among numerous cuprate superconductors and can serve as a prototypical system to explore the unconventional superconductivity.Based on the first-principles electronic structure calculations,we have studied the electronic and magnetic properties of the infinite-layer cuprate SrCuO_(2)from a phonon perspective.We find that interesting fluctuations of charges,electrical dipoles,and local magnetic moments can be induced by the atomic displacements of phonon modes in SrCuO_(2)upon the hole doping.Among all optical phonon modes of SrCuO_(2)in the antiferromagnetic Néel state,only the A_(1g)mode that involves the full-breathing O vibrations along the Cu-O bonds can cause significant fluctuations of local magnetic moments on O atoms and dramatic charge redistributions between Cu and O atoms.Notably,due to the atomic displacements of the A_(1g)mode,both the charge fluctuations on Cu and the electrical dipoles on O show a dome-like evolution with increasing hole doping,quite similar to the experimentally observed behavior of the superconducting T_(c);in comparison,the fluctuations of local magnetic moments on O display a monotonic enhancement along with the hole doping.Further analyses indicate that around the optimal doping,there exists a large softening in the frequency of the A_(1g)phonon mode and a van Hove singularity in the electronic structure close to the Fermi level,suggesting potential electron-phonon coupling.Our work reveals the important role of the full-breathing O phonon mode playing in the infinite-layer SrCuO_(2),which may provide new insights in understanding the cuprate superconductivity.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12174067 and 11804223)。
文摘We construct a three-dimensional topological superconductor Bogoliubov–de Gennes(BdG)Hamiltonian with the normal state being a three-dimensional topological insulator.By introducing inter-orbital spin-triplet pairings term△3,there are topological Majorana nodes in the bulk and they are connected by Majorana Fermi arcs on the surface,similar to the case of Weyl semimetal.Furthermore,by adding an inversion-breaking term to the normal state,momentum-independent pairing terms with different parities can coexist in the Bd G Hamiltonian,which creates more Majorana modes similar to Andreev bound states and a richer phase diagram.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12274439)the CAS Project for Young Scientists in Basic Research(Grant No.2022YSBR-048)。
文摘The remarkable electromagnetic characteristics inherent in unconventional superconductors have catalyzed the advance-ment of numerous technological innovations,spanning from energy-efficient power transmission and high-field magnets to sensitive detectors and quantum computing systems.Central to the functionality of these applications lies the superconducting characteristics,which govern pivotal phenomena including Cooper pair formation and macroscopic phase coherence,resulting in the attainment of zero electrical resistance,complete diamagnetism,and the Josephson tunneling effect.The complex phases and orders in these ma-terials significantly alter their key electronic and magnetic properties,posing challenges in elucidating the underlying physics and further enhancing their functional capabilities.The multiscale approach,representing a useful strategy for understanding materials across diverse length scales using a variety of experimental tools,can reveal intricate details in real and reciprocal spaces,facilitating cross-validation.In this brief review,we introduce the principle of the multiscale approach along with examples demonstrating its efficacy in unraveling the electronic and magnetic properties of unconventional superconductors.
