We systematically measure the superconducting(SC)and mixed state properties of high-quality CsV_3 Sb_5 single crystals with T_c-3.5 K.We find that the upper critical field H_(c2)(T)exhibits a large anisotropic ratio o...We systematically measure the superconducting(SC)and mixed state properties of high-quality CsV_3 Sb_5 single crystals with T_c-3.5 K.We find that the upper critical field H_(c2)(T)exhibits a large anisotropic ratio of H_(c2)^(ab)/H_(c2)^c^9 at zero temperature and fitting its temperature dependence requires a minimum two-band effective model.Moreover,the ratio of the lower critical field,H_(c1)^(ab)/H_(c1)^c,is also found to be larger than 1,which indicates that the in-plane energy dispersion is strongly renormalized near Fermi energy.Both H_(c1)(T)and SC diamagnetic signal are found to change little initially below T_c-3.5 K and then to increase abruptly upon cooling to a characteristic temperature of-2.8 K.Furthermore,we identify a two-fold anisotropy of in-plane angular-dependent magnetoresistance in the mixed state.Interestingly,we find that,below the same characteristic T-2.8 K,the orientation of this two-fold anisotropy displays a peculiar twist by an angle of 60°characteristic of the Kagome geometry.Our results suggest an intriguing superconducting state emerging in the complex environment of Kagome lattice,which,at least,is partially driven by electron-electron correlation.展开更多
Polycrystalline YBa2Cu3O7-y （YBCO） and Y0.6Gd0.4Ba2-xNbxCu3O7-y （YGBNCO） compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized b...Polycrystalline YBa2Cu3O7-y （YBCO） and Y0.6Gd0.4Ba2-xNbxCu3O7-y （YGBNCO） compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray difference （XRD） and scanning electron microscopy （SEM）. The transport properties were measured by the （FPP） method in the temperature range from 70 to 130 K. As the Nb content in the samples increased, a diffused phase indicating a niobium perovskite phase and a small amount of unidentified phase appeared. With the increase of Nb content, the superconducting transition temperature Tconset increased slowly with x≤0.125, and then it remained unchanged or slowly decreased with 0.125≤x≤0.225. It could be found that there was a slow decrease of zero-resistance temperature, Tcoffset, with the increase of Nb content. The larger transition width might result from the YBa2NbO6 phase, impurity and unidentified phases of the sample due to the Nb doping.展开更多
Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for...Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for high-temperature superconductors, as both Im3m YH_(6) and Im3m CaH_(6) exhibit similar structures and excellent superconducting properties, while Y and Ca atoms possess close atomic radii and electronegativities.Here, we report the successful synthesis of Im3m(Y, Ca)H_(6) achieving a maximum superconducting transition temperature(T_(c)) approximately 224 K at 155 GPa through five independent high-temperature and high-pressure experiments. Remarkably, the T_(c) of Im3m(Y, Ca)H_(6) remains highly stable(ΔT_(c) ≤ 1 K) during decompression between 148 and 165 GPa, significantly outperforming binary Im3m CaH_(6) and Im3m YH_(6). The enhanced superconducting properties may stem from the cooperative chemical template effect of Y and Ca atoms near the s-d border, which significantly reinforces H lattice stability and thus maintains superior superconductivity.This study highlights the potential of multicomponent cooperative effects in designing hydride superconductors,offering new insights for achieving high-T_(c) hydrides at lower pressures in the future.展开更多
The fabrication of high-quality YBa_(2)Cu_(3)O_(7)−δ(YBCO)nanowires has garnered significant attention in the field of high-temperature superconductivity due to their potential applications in quantum communication,d...The fabrication of high-quality YBa_(2)Cu_(3)O_(7)−δ(YBCO)nanowires has garnered significant attention in the field of high-temperature superconductivity due to their potential applications in quantum communication,deep space exploration,and various other fields.Cl_(2)-assisted reactive ion etching(RIE)stands out as a more effective and efficient method for patterning scalable thin films.However,neither RIE nor high-density RIE has achieved superconducting YBCO nanowires with a width smaller than 3μm.Here,we delve into the factors that limit the line width of Cl_(2)-assisted inductively coupled plasma reactive ion etching(ICP-RIE)processing and the method to elimiate them.Our approach involves utilizing Cl_(2)/Ar as etching gas and incorporating a specialized vacuum heating process after etching.Our experimental results demonstrate the successful realization of 10 nm-thick YBCO nanowires with widths as small as 0.15μm,exhibiting excellent performance in terms of their intrinsic superconducting properties.The mechanism is evidenced by X-ray photoelectron spectroscopy(XPS)analysis in comparison of nanowires with and without heating treatment,in which the residual Cl_(2) on the sidewall of nanowires evaporates and oxidizes Cu^(+)back into Cu^(2+)in an unetched state.展开更多
The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast s...The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT)growth.No signature of the electronic nematicity,but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples.Interestingly,a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se.Moreover,the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of-42 T,which breaks the Pauli limit by a factor of 1.8.展开更多
As one of the main materials in the practical application.of superconductor,lead(Pb)has been used to manufacture superconducting AC power cable,and some weak current fields.With the development of manufacturing,techno...As one of the main materials in the practical application.of superconductor,lead(Pb)has been used to manufacture superconducting AC power cable,and some weak current fields.With the development of manufacturing,technology,more and more researchers focus on exploring the physical and chemical properties of cryogenic superconducting materials,instead of blindly pursuing the improvement of the superconducting transition temperature(T_(c)).In this paper,the structural properties and superconducting transition temperature under high pressure of Pb have been studied by first-principles calculations.It has shown that Pb can withstand the compressive strain up to 10%while the lattice structure remains stable,indicated by the calculations of phonon band structures.From 0%to 10%compressive strain,there is neither a band-gap nor changing of the band structure.The.changing of electronic DOS.at the Fermi level leads to a decreasing of T_(c).Our calculations show that Pb is a stable elemental metallic superconductor even under high pressure,which explains the reason why it has been used in practical productions.展开更多
In this paper,we want to briefly review the progress of research on the properties of REBCO superconductor tapes,especially for the superconducting magnet.Firstly,we will introduce the progress of the RBcO super-condu...In this paper,we want to briefly review the progress of research on the properties of REBCO superconductor tapes,especially for the superconducting magnet.Firstly,we will introduce the progress of the RBcO super-conducting magnet.Then,we will discuss what kind of properties the REBCO superconducting magnet requires and their relevance.Based on these requirements,we individually introduce the research progress of these properties,including the measurement method,measurement equipment,data resources,and whether it is enough for the magnet design.We hope this paper can give initial guidance to the REBCO superconducting magnet designer and tape investigator on the properties of REBCO commercial tape.展开更多
The crystal structure and physical properties of Nb_(25)Mo_(5+x)Re_(35)Ru_(25-x)Rh_(10)(0≤x≤10)and Nb_(5)Mo_(35-y)Re_(15+y)Ru_(35)Rh_(10)(0≤y≤15)high-entropy alloys(HEAs)have been studied by X-ray diffraction,elec...The crystal structure and physical properties of Nb_(25)Mo_(5+x)Re_(35)Ru_(25-x)Rh_(10)(0≤x≤10)and Nb_(5)Mo_(35-y)Re_(15+y)Ru_(35)Rh_(10)(0≤y≤15)high-entropy alloys(HEAs)have been studied by X-ray diffraction,electrical resistivity,magnetic susceptibility,and specific heat measurements.The results show that the former HEAs with valence electron concentration(VEC)values of 6.7-6.9 crystallize in a noncentrosymmetric cubicα-Mn structure,while the latter ones with VEC values of 7.1-7.25 adopt a centrosymmetric hexagonal close-packed(hcp)structure.Despite different structures,both series of HEAs are found to be bulk superconductors with a full energy gap,and the superconducting transition temperature Tc tends to decrease with the increase of VEC.Nevertheless,the Tc values of the hcp-type HEAs are higher than those of theα-Mn-type ones,likely due to a stronger electron phonon coupling.Furthermore,we show that VEC and electronegativity difference are two key parameters to control the stability ofα-Mn and hcp-type HEAs.These results not only are helpful for the design of such HEAs,but also represent the first realization of structurally different HEA superconductors without changing the constituent elements.展开更多
Polycrystalline YBa2Cu3O6＋δbulks were synthesized by sol-gel method. Sintering processing played a vital role in the evolution of phase structure and microstructure, and thus significantly influenced their supercond...Polycrystalline YBa2Cu3O6＋δbulks were synthesized by sol-gel method. Sintering processing played a vital role in the evolution of phase structure and microstructure, and thus significantly influenced their superconducting properties. The influence of calcination temperature, sintering temperature, on the bulks structure, morphology and superconducting behaviors were investigated. The results showed that the oxygen content drastically increased with calcination temperature and sintering temperature. The SEM images revealed that the grains grew up monotonously with increase of calcination temperature. With increased calcination and sintering temperature, the resistivity was reduced gradually and the superconducting properties increased. Moreover, it was found that the optimal superconducting properties（with the highest superconducting transition temperature Tc^onset and the narrowest transition width ΔT） were obtained at calcination temperature of 900℃ and sintering temperature of 950 ℃.展开更多
Trigonal PtBi_(2)(γ-PtBi_(2))is a newly discovered polymorphic material with novel topological and superconducting properties[1,2].Due to its non-centrosymmetric structure,γ-PtBi_(2)hosts triply degenerate points an...Trigonal PtBi_(2)(γ-PtBi_(2))is a newly discovered polymorphic material with novel topological and superconducting properties[1,2].Due to its non-centrosymmetric structure,γ-PtBi_(2)hosts triply degenerate points and Weyl fermions[3–6].On the other hand,bulk superconductivity inγ-PtBi_(2)has been observed with a critical temperature Tc up to 0.6 K[7].Recent studies also uncover its surface superconductivity with Tc of 10 K[6,8].Therefore,γ-PtBi_(2),possessing non-trivial electronic topology and superconductivity,is a potential candidate for realizing the Fu-Kane topological superconductivity[6,9,10],which is timely needed to be further studied by low-temperature scanning tunneling microscopy(STM).However,as the first step,STM evidences of the topological surface states inγ-PtB_(2)are still lacking.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos.11834016,11888101,12061131005,51771224 and61888102)the National Key Research and Development Projects of China (Grant Nos.2017YFA0303003 and 2018YFA0305800)the Key Research Program and Strategic Priority Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant Nos.QYZDY-SSW-SLH001,XDB33010200 and XDB25000000)。
文摘We systematically measure the superconducting(SC)and mixed state properties of high-quality CsV_3 Sb_5 single crystals with T_c-3.5 K.We find that the upper critical field H_(c2)(T)exhibits a large anisotropic ratio of H_(c2)^(ab)/H_(c2)^c^9 at zero temperature and fitting its temperature dependence requires a minimum two-band effective model.Moreover,the ratio of the lower critical field,H_(c1)^(ab)/H_(c1)^c,is also found to be larger than 1,which indicates that the in-plane energy dispersion is strongly renormalized near Fermi energy.Both H_(c1)(T)and SC diamagnetic signal are found to change little initially below T_c-3.5 K and then to increase abruptly upon cooling to a characteristic temperature of-2.8 K.Furthermore,we identify a two-fold anisotropy of in-plane angular-dependent magnetoresistance in the mixed state.Interestingly,we find that,below the same characteristic T-2.8 K,the orientation of this two-fold anisotropy displays a peculiar twist by an angle of 60°characteristic of the Kagome geometry.Our results suggest an intriguing superconducting state emerging in the complex environment of Kagome lattice,which,at least,is partially driven by electron-electron correlation.
基金Project supported by the Council of the Scientific Research Projects at Konya University
文摘Polycrystalline YBa2Cu3O7-y （YBCO） and Y0.6Gd0.4Ba2-xNbxCu3O7-y （YGBNCO） compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray difference （XRD） and scanning electron microscopy （SEM）. The transport properties were measured by the （FPP） method in the temperature range from 70 to 130 K. As the Nb content in the samples increased, a diffused phase indicating a niobium perovskite phase and a small amount of unidentified phase appeared. With the increase of Nb content, the superconducting transition temperature Tconset increased slowly with x≤0.125, and then it remained unchanged or slowly decreased with 0.125≤x≤0.225. It could be found that there was a slow decrease of zero-resistance temperature, Tcoffset, with the increase of Nb content. The larger transition width might result from the YBa2NbO6 phase, impurity and unidentified phases of the sample due to the Nb doping.
基金supported by the National Key R&D Program of China (Grant No.2022YFA1405500)the National Natural Science Foundation of China (Grant No.52372257)。
文摘Ternary hydrides, with their superior chemical and structural flexibility over binary systems, open up new avenues for advancing high-performance superconductor research. The Y-Ca-H system is a promising candidate for high-temperature superconductors, as both Im3m YH_(6) and Im3m CaH_(6) exhibit similar structures and excellent superconducting properties, while Y and Ca atoms possess close atomic radii and electronegativities.Here, we report the successful synthesis of Im3m(Y, Ca)H_(6) achieving a maximum superconducting transition temperature(T_(c)) approximately 224 K at 155 GPa through five independent high-temperature and high-pressure experiments. Remarkably, the T_(c) of Im3m(Y, Ca)H_(6) remains highly stable(ΔT_(c) ≤ 1 K) during decompression between 148 and 165 GPa, significantly outperforming binary Im3m CaH_(6) and Im3m YH_(6). The enhanced superconducting properties may stem from the cooperative chemical template effect of Y and Ca atoms near the s-d border, which significantly reinforces H lattice stability and thus maintains superior superconductivity.This study highlights the potential of multicomponent cooperative effects in designing hydride superconductors,offering new insights for achieving high-T_(c) hydrides at lower pressures in the future.
基金supported by the National Key Research and Development Program of China(No.2021YFA0718800)the Natural Science Foundation of Sichuan Province(No.2023NSFSC0993)+1 种基金the National Natural Science Foundation of China(Nos.52021001,U22A20132 and 12074056)Sichuan Science and Technology Program(No.2021JDTD0010).
文摘The fabrication of high-quality YBa_(2)Cu_(3)O_(7)−δ(YBCO)nanowires has garnered significant attention in the field of high-temperature superconductivity due to their potential applications in quantum communication,deep space exploration,and various other fields.Cl_(2)-assisted reactive ion etching(RIE)stands out as a more effective and efficient method for patterning scalable thin films.However,neither RIE nor high-density RIE has achieved superconducting YBCO nanowires with a width smaller than 3μm.Here,we delve into the factors that limit the line width of Cl_(2)-assisted inductively coupled plasma reactive ion etching(ICP-RIE)processing and the method to elimiate them.Our approach involves utilizing Cl_(2)/Ar as etching gas and incorporating a specialized vacuum heating process after etching.Our experimental results demonstrate the successful realization of 10 nm-thick YBCO nanowires with widths as small as 0.15μm,exhibiting excellent performance in terms of their intrinsic superconducting properties.The mechanism is evidenced by X-ray photoelectron spectroscopy(XPS)analysis in comparison of nanowires with and without heating treatment,in which the residual Cl_(2) on the sidewall of nanowires evaporates and oxidizes Cu^(+)back into Cu^(2+)in an unetched state.
基金Supported by the National Key Research and Development Program of China (Grant Nos.2016YFA0300300 and 2017YFA0303003)the National Natural Science Foundation of China (Grant Nos.12061131005,11834016 and 11888101)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDB25000000)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant Nos.QYZDY-SSW-SLH001)。
文摘The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT)growth.No signature of the electronic nematicity,but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples.Interestingly,a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se.Moreover,the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of-42 T,which breaks the Pauli limit by a factor of 1.8.
文摘As one of the main materials in the practical application.of superconductor,lead(Pb)has been used to manufacture superconducting AC power cable,and some weak current fields.With the development of manufacturing,technology,more and more researchers focus on exploring the physical and chemical properties of cryogenic superconducting materials,instead of blindly pursuing the improvement of the superconducting transition temperature(T_(c)).In this paper,the structural properties and superconducting transition temperature under high pressure of Pb have been studied by first-principles calculations.It has shown that Pb can withstand the compressive strain up to 10%while the lattice structure remains stable,indicated by the calculations of phonon band structures.From 0%to 10%compressive strain,there is neither a band-gap nor changing of the band structure.The.changing of electronic DOS.at the Fermi level leads to a decreasing of T_(c).Our calculations show that Pb is a stable elemental metallic superconductor even under high pressure,which explains the reason why it has been used in practical productions.
基金funded by the National Natural Science Foundation of China(52293422,52293421,52325701,52422702,U23A6003)Beijing Municipal Natural Science Foundation(3232055).
文摘In this paper,we want to briefly review the progress of research on the properties of REBCO superconductor tapes,especially for the superconducting magnet.Firstly,we will introduce the progress of the RBcO super-conducting magnet.Then,we will discuss what kind of properties the REBCO superconducting magnet requires and their relevance.Based on these requirements,we individually introduce the research progress of these properties,including the measurement method,measurement equipment,data resources,and whether it is enough for the magnet design.We hope this paper can give initial guidance to the REBCO superconducting magnet designer and tape investigator on the properties of REBCO commercial tape.
基金financial support by the foundation of Westlake Universitysupported by the National Key Research Development Program of China(No.2017YFA0303002)。
文摘The crystal structure and physical properties of Nb_(25)Mo_(5+x)Re_(35)Ru_(25-x)Rh_(10)(0≤x≤10)and Nb_(5)Mo_(35-y)Re_(15+y)Ru_(35)Rh_(10)(0≤y≤15)high-entropy alloys(HEAs)have been studied by X-ray diffraction,electrical resistivity,magnetic susceptibility,and specific heat measurements.The results show that the former HEAs with valence electron concentration(VEC)values of 6.7-6.9 crystallize in a noncentrosymmetric cubicα-Mn structure,while the latter ones with VEC values of 7.1-7.25 adopt a centrosymmetric hexagonal close-packed(hcp)structure.Despite different structures,both series of HEAs are found to be bulk superconductors with a full energy gap,and the superconducting transition temperature Tc tends to decrease with the increase of VEC.Nevertheless,the Tc values of the hcp-type HEAs are higher than those of theα-Mn-type ones,likely due to a stronger electron phonon coupling.Furthermore,we show that VEC and electronegativity difference are two key parameters to control the stability ofα-Mn and hcp-type HEAs.These results not only are helpful for the design of such HEAs,but also represent the first realization of structurally different HEA superconductors without changing the constituent elements.
基金Project supported by the National Natural Science Foundation of China(11564021)
文摘Polycrystalline YBa2Cu3O6＋δbulks were synthesized by sol-gel method. Sintering processing played a vital role in the evolution of phase structure and microstructure, and thus significantly influenced their superconducting properties. The influence of calcination temperature, sintering temperature, on the bulks structure, morphology and superconducting behaviors were investigated. The results showed that the oxygen content drastically increased with calcination temperature and sintering temperature. The SEM images revealed that the grains grew up monotonously with increase of calcination temperature. With increased calcination and sintering temperature, the resistivity was reduced gradually and the superconducting properties increased. Moreover, it was found that the optimal superconducting properties（with the highest superconducting transition temperature Tc^onset and the narrowest transition width ΔT） were obtained at calcination temperature of 900℃ and sintering temperature of 950 ℃.
基金supported by the National Natural Science Foundation of China(92365201,12234011,12374053,12334003,and 52388201)the Ministry of Science and Technology of the People’s Republic of China(2022YFA1403100 and 2023YFA1406400)+6 种基金the Innovation Program for Quantum Science and Technology(2021ZD0302402)the National Key Research and Development Program of China(2022YFA1403400 and 2020YFA0308800)the Beijing National Laboratory for Condensed Matter Physics(2023BNLCMPKF007)the Beijing Natural Science Foundation(Z210006)supported by the Innovation Program for Quantum Science and Technology(2023ZD0300500)the National Science Fund for Distinguished Young Scholars(12025405)the Beijing Advanced Innovation Center for Future Chip(ICFC),and the Beijing Advanced Innovation Center for Materials Genome Engineering.
文摘Trigonal PtBi_(2)(γ-PtBi_(2))is a newly discovered polymorphic material with novel topological and superconducting properties[1,2].Due to its non-centrosymmetric structure,γ-PtBi_(2)hosts triply degenerate points and Weyl fermions[3–6].On the other hand,bulk superconductivity inγ-PtBi_(2)has been observed with a critical temperature Tc up to 0.6 K[7].Recent studies also uncover its surface superconductivity with Tc of 10 K[6,8].Therefore,γ-PtBi_(2),possessing non-trivial electronic topology and superconductivity,is a potential candidate for realizing the Fu-Kane topological superconductivity[6,9,10],which is timely needed to be further studied by low-temperature scanning tunneling microscopy(STM).However,as the first step,STM evidences of the topological surface states inγ-PtB_(2)are still lacking.
