Following the recent report by Dasenbrock-Gammon et al.[Nature 615,244–250(2023)]of near-ambient superconductivity in nitrogendoped lutetium trihydride(LuH_(3-δ)N_(ε)),significant debate has emerged surrounding the...Following the recent report by Dasenbrock-Gammon et al.[Nature 615,244–250(2023)]of near-ambient superconductivity in nitrogendoped lutetium trihydride(LuH_(3-δ)N_(ε)),significant debate has emerged surrounding the composition and interpretation of the observed sharp resistance drop.Here,we meticulously revisit these claims through comprehensive characterization and investigations.We definitively identify the reported material as lutetium dihydride(LuH_(2)),resolving the ambiguity surrounding its composition.Under similar conditions(270–295 K and 1–2 GPa),we replicate the reported sharp decrease in electrical resistance with a 30%success rate,aligning with the observations by Dasenbrock-Gammon et al.However,our extensive investigations reveal this phenomenon to be a novel pressure-induced metal-to-metal transition intrinsic to LuH_(2),distinct from superconductivity.Intriguingly,nitrogen doping exerts minimal impact on this transition.Our work not only elucidates the fundamental properties of LuH_(2)andLuH_(3),but also critically challenges the notion of superconductivity in these lutetium hydride systems.These findings pave the way for future research on lutetium hydride systems,while emphasizing the crucial importance of rigorous verification in claims of ambient-temperature superconductivity.展开更多
Background:People with atrial fibrillation(AF)have elevated risk of developing cognitive impairment.At present,there is a dearth of randomized controlled trials investigating cognitive impairment management in patient...Background:People with atrial fibrillation(AF)have elevated risk of developing cognitive impairment.At present,there is a dearth of randomized controlled trials investigating cognitive impairment management in patients with AF.The Atrial Fibrillation Follow-up Investigation to Recover Memory and learning(AFFIRMING)study is aimed at evaluating the potential for computerized cognitive training to improve cognitive function in patients with AF.Methods:The study is a multi-center,double-blind,randomized controlled study using a 1:1 parallel design.A total of 200 patients with AF and mild cognitive decline without dementia are planned to be recruited.The intervention group will use the adaptive training software with changes in difficulty,whereas the positive control group will use basic training software with minimal or no variation in difficulty level.At the end of 12 weeks,the participants will be unblinded,and the positive control group will stop training.The intervention group will be rerandomized 1:1 to stop training or continue training.All participants will be followed up until 24 weeks.The primary endpoint is the propor-tion of the improvement of the global cognitive function at week 12 compared with baseline,using the Basic Cognitive Ability Test(BCAT).展开更多
Transition metal dichalcogenides, featuring layered structures, have aroused enormous interest as a platform for novel physical phenomena and a wide range of potential applications. Among them, special interest has be...Transition metal dichalcogenides, featuring layered structures, have aroused enormous interest as a platform for novel physical phenomena and a wide range of potential applications. Among them, special interest has been placed upon WTe_2 and MoTe_2, which exhibit non-trivial topology both in single layer and bulk as well as pressure induced or enhanced superconductivity. We study another distorted IT material NbTe_2 through systematic electrical transport measurements. Intrinsic superconductivity with onset transition temperature(T_c^(onset)) up to 0.72 K is detected where the upper critical field(H_c) shows unconventional quasi-linear behavior,indicating spin-orbit coupling induced p-wave paring. Furthermore, a general model is proposed to fit the angledependent magnetoresistance, which reveals the Fermi surface anisotropy of NbTe_2. Finally, non-saturating linear magnetoresistance up to 50 T is observed and attributed to the quantum limit transport.展开更多
A material described as lutetium–hydrogen–nitrogen(Lu-H-N in short)was recently claimed to have“near-ambient superconductivity”[Dasenbrock-Gammon et al.,Nature 615,244–250(2023)].If this result could be reproduce...A material described as lutetium–hydrogen–nitrogen(Lu-H-N in short)was recently claimed to have“near-ambient superconductivity”[Dasenbrock-Gammon et al.,Nature 615,244–250(2023)].If this result could be reproduced by other teams,it would be a major scientific breakthrough.Here,we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al.Our x-ray diffraction measurements indicate that the obtained sample contains three substances:the facecentered-cubic(FCC)-1 phase(Fm-3m)with lattice parameter a=5.03Å,the FCC-2 phase(Fm-3m)with a lattice parameter a=4.755Å,and Lu metal.The two FCC phases are identical to the those reported in the so-called near-ambient superconductor.However,we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity.We also use a laser heating technique to heat a sample to 1800 XC and find no superconductivity in the produced dark blue material below 6.5 GPa.In addition,both samples remain dark blue in color in the pressure range investigated.展开更多
We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Con...We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Condition User Facilities in the Huairou District of Beijing, China. To demonstrate the capabilities of the system for condensed matter research, the emergence of some pressure-induced phenomena and physics related to superconductivity found previously is also introduced, and then a perspective for such an advanced high-pressure system is presented.展开更多
The microstructure development of Pd77.5Au6Si16.5 alloy droplet solidified in a drop tube process was studied. It was found that two distinct microstructures, i.e. (Pd,Au)3Si primary phase and Pd+(Pd,Au)3Si eutectic c...The microstructure development of Pd77.5Au6Si16.5 alloy droplet solidified in a drop tube process was studied. It was found that two distinct microstructures, i.e. (Pd,Au)3Si primary phase and Pd+(Pd,Au)3Si eutectic can be obtained when the droplet diameter is within the range between 2.3~0.4 mm. The morpologies of the (Pd,Au)3Si developed from dendrite trunk-like with single branching only into dendrite cluster-like with ternary branching with the decrease of the droplet diameter. When the droplet diameter is about 0.25 mm, the primary phase (Pd,Au)3Si almost disappears and the microstructure mainly shows Pd+(Pd,Au)3Si eutectic. The morphology of the eutectic transforms from fiber-like to plate-like with the decrease of the droplet diameter in the range between 2.3-0.25 mm. When the droplet diameter is about 0.19 mm, the microstructure is only the single phase of Pd solid solution展开更多
We investigate the uniaxial-pressure dependence of resistivity for URu_(2−x)Fe_(x)Si_(2)samples with x=0 and 0.2,which host a hidden order(HO)and a large-moment antiferromagnetic(LMAFM)phase,respectively.For both samp...We investigate the uniaxial-pressure dependence of resistivity for URu_(2−x)Fe_(x)Si_(2)samples with x=0 and 0.2,which host a hidden order(HO)and a large-moment antiferromagnetic(LMAFM)phase,respectively.For both samples,the elastoresistivityζshows a seemingly divergent behavior above the transition temperature T_(0)and a quick decrease below it.We find that the temperature dependence ofζfor both samples can be well described by assuming the uniaxial pressure effect on the gap or certain energy scale except forζ(110)of the x=0 sample,which exhibits a nonzero residual value at 0 K.We show that this provides a qualitative difference between the HO and LMAFM phases.Our results suggest that there is an in-plane anisotropic response to the uniaxial pressure that only exists in the hidden order state without necessarily breaking the rotational lattice symmetry.展开更多
The dissipation theory was introduced into the solidification area to describe the inherent laws of solidification from a new viewpoint. Discussion demonstrates that the solid / liquid interface in a directionally sol...The dissipation theory was introduced into the solidification area to describe the inherent laws of solidification from a new viewpoint. Discussion demonstrates that the solid / liquid interface in a directionally solidified alloy belongs to a kind of dissipation structure展开更多
The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications.Nb_(3)Sn,an intermetallic alloy with an A15 structure,is a key commercial superconducto...The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications.Nb_(3)Sn,an intermetallic alloy with an A15 structure,is a key commercial superconductor known for its high critical current and magnetic field tolerance.Here,we systematically investigated the physical properties of Nb_(3)Sn under high pressures.Our findings reveal that superconductivity in Nb_(3)Sn remains robust up to∼142 GPa,demonstrating remarkable stability despite a gradual suppression of��c with increasing pressure.First-principles calculations indicate that the pressure-dependent superconducting behavior is primarily driven by variations in the density of states of Nb’s d-electrons,particularly contributions from the d_(x^(2)-y^(2)) and d_(z^(2)) orbitals.Furthermore,we predict the potential for synthesizing Nb_(3)Sn films and demonstrate that biaxial strain induced by suitable substrates can preserve their superconducting properties.This comprehensive study not only enhances our understanding of Nb_(3)Sn’s superconducting mechanism under high pressure but also opens new avenues for its application in advanced superconducting technologies.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 ofρ_(s)andσwith 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)andσ,respectively,implying that the physics determining T_(c)is governed by the intrinsic electromagnetic fields of the system.展开更多
The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges.The high-pressure exper-imental setup makes it difficult to directly measure the size changes induced...The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges.The high-pressure exper-imental setup makes it difficult to directly measure the size changes induced by pressure in the three crystallographic directions of the sample.In this study,we introduce a novel and effective method that addresses these technical challenges.This method is anticipated to offer a valuable foundation for high-pressure investigations on quantum materials,particularly those with anisotropic layered structures.展开更多
Signatures of superconductivity near 80 K have recently been discovered in single crystals of La_(3)Ni_(2)O_(7)under pressure,which makes it a new candidate for high-temperature superconductors dominated by 3d transit...Signatures of superconductivity near 80 K have recently been discovered in single crystals of La_(3)Ni_(2)O_(7)under pressure,which makes it a new candidate for high-temperature superconductors dominated by 3d transition elements,following the cuprate and iron-pnictide superconductors.However,there are several critical questions that have been perplexing the scientificommunity:(1)What factors contribute to the inconsistent reproducibility of the experimental results?(2)What is the fundamental nature of pressure-induced superconductivity:bulk or nonbulk(filamentary-like)(3)Where is the superconducting phase located within the sample if it is filamentary-like(4)Is the oxygen content important for the development and stabilization of superconductivity?In this study,we employ comprehensive high-pressure techniques to address these questions.Through our modulated ac susceptibility measurements,we are the firs to fin that the superconductivity in this nickelate is filamentary-like Our scanning transmission electron microscopy investigations suggest that the filamentary-lik superconductivity most likely emerges at the interface between La_(3)Ni_(2)O_(7)and La_(4)Ni_(3)O_(10)phases.By tuning the oxygen content of polycrystalline La_(3)Ni_(2)O_(7),we also fin that it plays vital role in the development and stabilization of superconductivity in this material.The upper and lower bounds on the oxygen content are 7.35 and 6.89,respectively.Our results provide not only new insights into the puzzling issues regarding this material,but also significan information that will enable a better understanding of its superconductivity.展开更多
The notion of the Ricci curvature is defined for sprays on a manifold.With a volume form on a manifold,every spray can be deformed to a projective spray.The Ricci curvature of a projective spray is called the projecti...The notion of the Ricci curvature is defined for sprays on a manifold.With a volume form on a manifold,every spray can be deformed to a projective spray.The Ricci curvature of a projective spray is called the projective Ricci curvature.In this paper,we introduce the notion of projectively Ricci-flat sprays.We establish a global rigidity result for projectively Ricci-flat sprays with nonnegative Ricci curvature.Then we study and characterize projectively Ricci-flat Randers metrics.展开更多
Let （E, F） be a complex Finsler vector bundle over a compact Kahler manifold （M, g） with Kahler form φ We prove that if （E, F） is a weakly complex Einstein-Finsler vector bundle in the sense of Aikou （1997）, ...Let （E, F） be a complex Finsler vector bundle over a compact Kahler manifold （M, g） with Kahler form φ We prove that if （E, F） is a weakly complex Einstein-Finsler vector bundle in the sense of Aikou （1997）, then it is modeled on a complex Minkowski space. Consequently, a complex Einstein-Finsler vector bundle （E, F） over a compact Kahler manifold （M, g） is necessarily φ-semistable and （E,F）=（E1,F1）……（Ek,Fk）,where Fj ：= F｜Ej, and each （Ej, Fj） is modeled on a complex Minkowski space whose associated Hermitian vector bundle is a φ-stable Einstein-Hermitian vector bundle with the same factor c as （E, F）.展开更多
One of the most strikingly universal features of the high-temperature superconductors is that the super- conducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these ...One of the most strikingly universal features of the high-temperature superconductors is that the super- conducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these two phases poses a long-standing challenge. It is commonly believed that, as the antifer- romagnetic transition temperature is continuously suppressed to zero, there appears a quantum critical point, around which the existence of antiferromagnetic fluctuation is responsible for the development of the superconductivity. In contrast to this scenario, we report the observation of a bi-critical point identified at 2,88 GPa and 26.02 K in the pressurized high-quality single crystal Cao.73Lao.27FeAs2 by com- plementary in-situ high pressure measurements. At the critical pressure, we find that the antiferromag- netism suddenly disappears and superconductivity simultaneously emerges at almost the same temperature, and that the external magnetic field suppresses the superconducting transition temperature but hardly affects the antiferromagnetic transition temperature.展开更多
SmB_6 has been a well-known Kondo insulator for decades, but recently attracts extensive new attention as a candidate topological system. Studying SmB_6 under pressure provides an opportunity to acquire the much-neede...SmB_6 has been a well-known Kondo insulator for decades, but recently attracts extensive new attention as a candidate topological system. Studying SmB_6 under pressure provides an opportunity to acquire the much-needed understanding about the effect of electron correlations on both the metallic surface state and bulk insulating state. Here we do so by studying the evolution of two transport gaps(low temperature gap E_l and high temperature gap E_h) associated with the Kondo effect by measuring the electrical resistivity under high pressure and low temperature(0.3 K) conditions. We associate the gaps with the bulk Kondo hybridization, and from their evolution with pressure we demonstrate an insulator-tometal transition at ~4 GPa. At the transition pressure, a large change in the Hall number and a divergence tendency of the electron-electron scattering coefficient provide evidence for a destruction of the Kondo entanglement in the ground state. Our results raise the new prospect for studying topological electronic states in quantum critical materials settings.展开更多
基金the National Key Research and Development Program of China(Grant Nos.2022YFA1402301 and 2018YFA0305703)the National Natural Science Foundation of China(Grant No.U2230401)+2 种基金the National Key R&D Program of China(Grant No.2021YFA1400200),the National Natural Science Foundation of China(Grant Nos.12025408 and 11921004)the Strategic Priority Research Program of CAS(Grant No.XDB33000000).
文摘Following the recent report by Dasenbrock-Gammon et al.[Nature 615,244–250(2023)]of near-ambient superconductivity in nitrogendoped lutetium trihydride(LuH_(3-δ)N_(ε)),significant debate has emerged surrounding the composition and interpretation of the observed sharp resistance drop.Here,we meticulously revisit these claims through comprehensive characterization and investigations.We definitively identify the reported material as lutetium dihydride(LuH_(2)),resolving the ambiguity surrounding its composition.Under similar conditions(270–295 K and 1–2 GPa),we replicate the reported sharp decrease in electrical resistance with a 30%success rate,aligning with the observations by Dasenbrock-Gammon et al.However,our extensive investigations reveal this phenomenon to be a novel pressure-induced metal-to-metal transition intrinsic to LuH_(2),distinct from superconductivity.Intriguingly,nitrogen doping exerts minimal impact on this transition.Our work not only elucidates the fundamental properties of LuH_(2)andLuH_(3),but also critically challenges the notion of superconductivity in these lutetium hydride systems.These findings pave the way for future research on lutetium hydride systems,while emphasizing the crucial importance of rigorous verification in claims of ambient-temperature superconductivity.
基金funded by Capital’s Funds for Health Improvement and Research,grant/award number 2022-2-2067The trial is supported by the Science and Technology Foundation of Beijing Anzhen Hospital,Capital Medical University,grant/award number:KCGY2022.
文摘Background:People with atrial fibrillation(AF)have elevated risk of developing cognitive impairment.At present,there is a dearth of randomized controlled trials investigating cognitive impairment management in patients with AF.The Atrial Fibrillation Follow-up Investigation to Recover Memory and learning(AFFIRMING)study is aimed at evaluating the potential for computerized cognitive training to improve cognitive function in patients with AF.Methods:The study is a multi-center,double-blind,randomized controlled study using a 1:1 parallel design.A total of 200 patients with AF and mild cognitive decline without dementia are planned to be recruited.The intervention group will use the adaptive training software with changes in difficulty,whereas the positive control group will use basic training software with minimal or no variation in difficulty level.At the end of 12 weeks,the participants will be unblinded,and the positive control group will stop training.The intervention group will be rerandomized 1:1 to stop training or continue training.All participants will be followed up until 24 weeks.The primary endpoint is the propor-tion of the improvement of the global cognitive function at week 12 compared with baseline,using the Basic Cognitive Ability Test(BCAT).
基金Supported by the National Basic Research Program of China under Grant Nos 2018YFA0305600 and 2017YFA0303302the National Natural Science Foundation of China under Grant Nos 11888101,11774008,11704414 and 11427805+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB28000000Beijing Natural Science Foundation(Z180010)
文摘Transition metal dichalcogenides, featuring layered structures, have aroused enormous interest as a platform for novel physical phenomena and a wide range of potential applications. Among them, special interest has been placed upon WTe_2 and MoTe_2, which exhibit non-trivial topology both in single layer and bulk as well as pressure induced or enhanced superconductivity. We study another distorted IT material NbTe_2 through systematic electrical transport measurements. Intrinsic superconductivity with onset transition temperature(T_c^(onset)) up to 0.72 K is detected where the upper critical field(H_c) shows unconventional quasi-linear behavior,indicating spin-orbit coupling induced p-wave paring. Furthermore, a general model is proposed to fit the angledependent magnetoresistance, which reveals the Fermi surface anisotropy of NbTe_2. Finally, non-saturating linear magnetoresistance up to 50 T is observed and attributed to the quantum limit transport.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the NSF of China(Grant Nos.U2032214,12104487,12122414,and 12004419)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)J.G.and S.C.are grateful for support from the Youth Innovation Promotion Association of the CAS(Grant No.2019008)the China Postdoctoral Science Foundation(Grant No.E0BK111).
文摘A material described as lutetium–hydrogen–nitrogen(Lu-H-N in short)was recently claimed to have“near-ambient superconductivity”[Dasenbrock-Gammon et al.,Nature 615,244–250(2023)].If this result could be reproduced by other teams,it would be a major scientific breakthrough.Here,we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al.Our x-ray diffraction measurements indicate that the obtained sample contains three substances:the facecentered-cubic(FCC)-1 phase(Fm-3m)with lattice parameter a=5.03Å,the FCC-2 phase(Fm-3m)with a lattice parameter a=4.755Å,and Lu metal.The two FCC phases are identical to the those reported in the so-called near-ambient superconductor.However,we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity.We also use a laser heating technique to heat a sample to 1800 XC and find no superconductivity in the produced dark blue material below 6.5 GPa.In addition,both samples remain dark blue in color in the pressure range investigated.
文摘We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Condition User Facilities in the Huairou District of Beijing, China. To demonstrate the capabilities of the system for condensed matter research, the emergence of some pressure-induced phenomena and physics related to superconductivity found previously is also introduced, and then a perspective for such an advanced high-pressure system is presented.
文摘The microstructure development of Pd77.5Au6Si16.5 alloy droplet solidified in a drop tube process was studied. It was found that two distinct microstructures, i.e. (Pd,Au)3Si primary phase and Pd+(Pd,Au)3Si eutectic can be obtained when the droplet diameter is within the range between 2.3~0.4 mm. The morpologies of the (Pd,Au)3Si developed from dendrite trunk-like with single branching only into dendrite cluster-like with ternary branching with the decrease of the droplet diameter. When the droplet diameter is about 0.25 mm, the primary phase (Pd,Au)3Si almost disappears and the microstructure mainly shows Pd+(Pd,Au)3Si eutectic. The morphology of the eutectic transforms from fiber-like to plate-like with the decrease of the droplet diameter in the range between 2.3-0.25 mm. When the droplet diameter is about 0.19 mm, the microstructure is only the single phase of Pd solid solution
基金supported by the National Key Research and Development Program of China(Grant Nos.2020YFA0406003,2021YFA1400401,2017YFA0302903,and 2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.11961160699,11874401,and 11974397)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB33000000 and XDB25000000)the K.C.Wong Education Foundation(Grant No.GJTD2020-01).
文摘We investigate the uniaxial-pressure dependence of resistivity for URu_(2−x)Fe_(x)Si_(2)samples with x=0 and 0.2,which host a hidden order(HO)and a large-moment antiferromagnetic(LMAFM)phase,respectively.For both samples,the elastoresistivityζshows a seemingly divergent behavior above the transition temperature T_(0)and a quick decrease below it.We find that the temperature dependence ofζfor both samples can be well described by assuming the uniaxial pressure effect on the gap or certain energy scale except forζ(110)of the x=0 sample,which exhibits a nonzero residual value at 0 K.We show that this provides a qualitative difference between the HO and LMAFM phases.Our results suggest that there is an in-plane anisotropic response to the uniaxial pressure that only exists in the hidden order state without necessarily breaking the rotational lattice symmetry.
文摘The dissipation theory was introduced into the solidification area to describe the inherent laws of solidification from a new viewpoint. Discussion demonstrates that the solid / liquid interface in a directionally solidified alloy belongs to a kind of dissipation structure
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1401800 and 2022YFA1403900)the NSF of China(Grant Numbers Grants No.12122414,12474054,U2032214 and 12122405)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)the Fundamental Research Funds for the Central Universities,China.
文摘The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications.Nb_(3)Sn,an intermetallic alloy with an A15 structure,is a key commercial superconductor known for its high critical current and magnetic field tolerance.Here,we systematically investigated the physical properties of Nb_(3)Sn under high pressures.Our findings reveal that superconductivity in Nb_(3)Sn remains robust up to∼142 GPa,demonstrating remarkable stability despite a gradual suppression of��c with increasing pressure.First-principles calculations indicate that the pressure-dependent superconducting behavior is primarily driven by variations in the density of states of Nb’s d-electrons,particularly contributions from the d_(x^(2)-y^(2)) and d_(z^(2)) orbitals.Furthermore,we predict the potential for synthesizing Nb_(3)Sn films and demonstrate that biaxial strain induced by suitable substrates can preserve their superconducting properties.This comprehensive study not only enhances our understanding of Nb_(3)Sn’s superconducting mechanism under high pressure but also opens new avenues for its application in advanced superconducting technologies.
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 ofρ_(s)andσwith 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)andσ,respectively,implying that the physics determining T_(c)is governed by the intrinsic electromagnetic fields of the system.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the NSF of China(Grant Nos.U2032214 and 12104487).
文摘The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges.The high-pressure exper-imental setup makes it difficult to directly measure the size changes induced by pressure in the three crystallographic directions of the sample.In this study,we introduce a novel and effective method that addresses these technical challenges.This method is anticipated to offer a valuable foundation for high-pressure investigations on quantum materials,particularly those with anisotropic layered structures.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the NSF of China(Grant Nos.U2032214,12122414,12104487,and 12004419)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)support from the Youth Innovation Promotion Association of the CAS(2019008)supported by the Synergetic Extreme Condition User Facility(SECUF)。
文摘Signatures of superconductivity near 80 K have recently been discovered in single crystals of La_(3)Ni_(2)O_(7)under pressure,which makes it a new candidate for high-temperature superconductors dominated by 3d transition elements,following the cuprate and iron-pnictide superconductors.However,there are several critical questions that have been perplexing the scientificommunity:(1)What factors contribute to the inconsistent reproducibility of the experimental results?(2)What is the fundamental nature of pressure-induced superconductivity:bulk or nonbulk(filamentary-like)(3)Where is the superconducting phase located within the sample if it is filamentary-like(4)Is the oxygen content important for the development and stabilization of superconductivity?In this study,we employ comprehensive high-pressure techniques to address these questions.Through our modulated ac susceptibility measurements,we are the firs to fin that the superconductivity in this nickelate is filamentary-like Our scanning transmission electron microscopy investigations suggest that the filamentary-lik superconductivity most likely emerges at the interface between La_(3)Ni_(2)O_(7)and La_(4)Ni_(3)O_(10)phases.By tuning the oxygen content of polycrystalline La_(3)Ni_(2)O_(7),we also fin that it plays vital role in the development and stabilization of superconductivity in this material.The upper and lower bounds on the oxygen content are 7.35 and 6.89,respectively.Our results provide not only new insights into the puzzling issues regarding this material,but also significan information that will enable a better understanding of its superconductivity.
文摘The notion of the Ricci curvature is defined for sprays on a manifold.With a volume form on a manifold,every spray can be deformed to a projective spray.The Ricci curvature of a projective spray is called the projective Ricci curvature.In this paper,we introduce the notion of projectively Ricci-flat sprays.We establish a global rigidity result for projectively Ricci-flat sprays with nonnegative Ricci curvature.Then we study and characterize projectively Ricci-flat Randers metrics.
基金supported by National Natural Science Foundation of China(Grant Nos.11671330 and 11271304)the Fujian Province Natural Science Funds for Distinguished Young Scholar(Grant No.2013J06001)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘Let （E, F） be a complex Finsler vector bundle over a compact Kahler manifold （M, g） with Kahler form φ We prove that if （E, F） is a weakly complex Einstein-Finsler vector bundle in the sense of Aikou （1997）, then it is modeled on a complex Minkowski space. Consequently, a complex Einstein-Finsler vector bundle （E, F） over a compact Kahler manifold （M, g） is necessarily φ-semistable and （E,F）=（E1,F1）……（Ek,Fk）,where Fj ：= F｜Ej, and each （Ej, Fj） is modeled on a complex Minkowski space whose associated Hermitian vector bundle is a φ-stable Einstein-Hermitian vector bundle with the same factor c as （E, F）.
基金supported by the National Natural Science Foundation of China(91321207,11427805,U1532267,11404384)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB07020300)+2 种基金the National Key Research and Development Program of China(2016YFA0300300)the Russian Foundation for Basic Research(15-02-02040)the U.S.NSF DMREF(DMR-1435672)
文摘One of the most strikingly universal features of the high-temperature superconductors is that the super- conducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these two phases poses a long-standing challenge. It is commonly believed that, as the antifer- romagnetic transition temperature is continuously suppressed to zero, there appears a quantum critical point, around which the existence of antiferromagnetic fluctuation is responsible for the development of the superconductivity. In contrast to this scenario, we report the observation of a bi-critical point identified at 2,88 GPa and 26.02 K in the pressurized high-quality single crystal Cao.73Lao.27FeAs2 by com- plementary in-situ high pressure measurements. At the critical pressure, we find that the antiferromag- netism suddenly disappears and superconductivity simultaneously emerges at almost the same temperature, and that the external magnetic field suppresses the superconducting transition temperature but hardly affects the antiferromagnetic transition temperature.
基金supported by the National Key Research and Development Program of China(2017YFA0302900,2016YFA0300300 and 2015CB921303)the National Natural Science Foundation of China(91321207,11427805,11404384,U1532267 and 11522435)+8 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB07020300 and XDB07020200)supported by the National Natural Science Foundation of China(1374361)the National Key Research and Development Program of China(2016YFA0300300)the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(14XNLF08)funded by the Los Alamos LDRD programthe FAPESP Grant 2013/2018-0supported by the ARO Grant No.W911NF-14-10525the Robert A.Welch Foundation Grant No.C-1411
文摘SmB_6 has been a well-known Kondo insulator for decades, but recently attracts extensive new attention as a candidate topological system. Studying SmB_6 under pressure provides an opportunity to acquire the much-needed understanding about the effect of electron correlations on both the metallic surface state and bulk insulating state. Here we do so by studying the evolution of two transport gaps(low temperature gap E_l and high temperature gap E_h) associated with the Kondo effect by measuring the electrical resistivity under high pressure and low temperature(0.3 K) conditions. We associate the gaps with the bulk Kondo hybridization, and from their evolution with pressure we demonstrate an insulator-tometal transition at ~4 GPa. At the transition pressure, a large change in the Hall number and a divergence tendency of the electron-electron scattering coefficient provide evidence for a destruction of the Kondo entanglement in the ground state. Our results raise the new prospect for studying topological electronic states in quantum critical materials settings.
