Bi-based 2223 superconducting tapes with high critical current densities were prepared by silver-sheathingmethod.The relationship between processing,microstructure and property was discussed.The results of criti-cal c...Bi-based 2223 superconducting tapes with high critical current densities were prepared by silver-sheathingmethod.The relationship between processing,microstructure and property was discussed.The results of criti-cal current density measurement at 77.7 K with different applied magnetic field are as follows:j_e=2.87×10~4A/cm^2(OT),J_e=4100 A/cm^2(H I.H||S.1T)and J_e-B characteristics are obviously improved withtemperature decreasing from 77 K to 4.2 K.Microstructtlre observations indicate that intermediate pressingwith subsequent heat-trcating could lower the porosity of superconductor inside the silver sheath,and reducethe amount and size of non-superconducting phases,leading phases,leading to the formation of a strong c-axis-orientedtexture,and the emergence of high dislocation density within the 2223 grains,and consequently the J(?)andJ_e-B characteritics were improved.展开更多
Triangular antidot lattices of various periods and aspect ratios are fabricated on high mobility GaAs/AlGaAs two-dimensional electron systems(2DESs),and are characterized by magneto-transport measurements at low tempe...Triangular antidot lattices of various periods and aspect ratios are fabricated on high mobility GaAs/AlGaAs two-dimensional electron systems(2DESs),and are characterized by magneto-transport measurements at low temperatures down to 300 mK. Commensurability peaks are generally observed in the magneto-resistivity ρ_(xx),and remarkable similarity between dρ_(xy)/dB and ρ_(xx) is found. In samples of relatively large aspect ratio d/a, the Aharonov-Bohm-type oscillations are clearly observed in both ρ_(xx) and ρ_(xy), as well as the quenching of the Hall resistivity ρ_(xy) in the vicinity of B = 0. These observations evince the good quality of our samples, and attest to the adequate preparation for fabricating antidot lattices of a reduced period to realize artificial graphene from GaAs/AlGaAs 2DESs.展开更多
Electronic transports of few-layer 1T'-MoTe_2 films are measured at temperatures down to 0.26 K. The lowtemperature conductivity exhibits logarithmic temperature dependence and negative magneto response. The negat...Electronic transports of few-layer 1T'-MoTe_2 films are measured at temperatures down to 0.26 K. The lowtemperature conductivity exhibits logarithmic temperature dependence and negative magneto response. The negative magnetoconductivity can be well fitted by the two-dimensional weak anti-localization theory taking a single channel of electrons into account, with the parameters α≈-0.5 and l_φ∝ T^(-0 5). The logarithmic temperature dependence has a positive slope κ≈0.75, indicating the dominance of electron-electron interaction over the weak anti-localization effect, with an apparently negative Coulomb screening factor F that demands future work for clarification.展开更多
The Institute of Physics, Chinese Academy of Sciences, is in charge of the construction of the Synergetic Extreme Condition User Facility(SECUF) in Huairou, Beijing. The SECUF is a comprehensive facility focused on pr...The Institute of Physics, Chinese Academy of Sciences, is in charge of the construction of the Synergetic Extreme Condition User Facility(SECUF) in Huairou, Beijing. The SECUF is a comprehensive facility focused on providing extreme physical conditions for scientific research, including an ultralow temperature, ultrahigh pressure, ultrahigh magnetic field, and ultrafast laser. The ultralow temperature will be realized by the sub-millikelvin(sub-mK) station, whose main component is an adiabatic nuclear demagnetization refrigerator(ANDR). The refrigerator is designed to have a base temperature below 1 mK and a magnetic field up to 16 T for experiments, as well as a characteristic parameter of B/T≥10~4 T/K.In this review, we introduce adiabatic nuclear demagnetization refrigeration, thermometry from 10 mK to sub-mK, the properties and parameters of the ANDR of the SECUF, and related prospective research topics.展开更多
There is no consensus whether the electron density of states of decagonal quasicrystals has a pseudogap at the Fermi energy similar to that of the icosahedron phase. We answer this question by measuring the electronic...There is no consensus whether the electron density of states of decagonal quasicrystals has a pseudogap at the Fermi energy similar to that of the icosahedron phase. We answer this question by measuring the electronic specific heat coefficient of AlCuCo decagonal single-quasicrystals over a wide range of composition. While the average valence electron number per atom, e/a, for all the resultant samples changes only within 1.5%, from-1.92 to less than 1.95. The specific heat coefficient decreases by 15% with the increasing e/a. The large change and the negative slope give strong evidence for Hume-Rothery mechanism of the decagonal phase.展开更多
Full gap closing is a prerequisite for hosting Majorana zero modes in Josephson junctions on the surface of topological insulators.Previously,we have observed direct experimental evidence of gap closing in Josephson j...Full gap closing is a prerequisite for hosting Majorana zero modes in Josephson junctions on the surface of topological insulators.Previously,we have observed direct experimental evidence of gap closing in Josephson junctions constructed on Bi_2Te_3 surface.In this paper we report further investigations on the position dependence of gap closing as a function of magnetic flux in single Josephson junctions constructed on Bi_2Te_3 surface.展开更多
We report on magnetoresistance, Hall effect, and quantum Shubnikov–de Haas oscillation(SdH) experiments in NbIrTe4 single crystals, which was recently predicted to be a type-II Weyl semimetal. NbIrTe4 manifests a non...We report on magnetoresistance, Hall effect, and quantum Shubnikov–de Haas oscillation(SdH) experiments in NbIrTe4 single crystals, which was recently predicted to be a type-II Weyl semimetal. NbIrTe4 manifests a non-saturating and parabolic magnetoresistance at low temperatures. The magneto-transport measurements show that NbIrTe4 is a multiband system. The analysis of the SdH oscillations reveals four distinct oscillation frequencies. Combined with the density-functional theory calculations, we show that they come from two types of Fermi surfaces: electron pocket E1 and hole pocket H2.展开更多
Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells.The low-temperature longitudinal resistivity(ρ_(xx))data demonstrate that ...Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells.The low-temperature longitudinal resistivity(ρ_(xx))data demonstrate that a striking even-odd asymmetric transport exists along the [110] direction at half filling in N > 2 high Landau levels.Although the origin for the peculiar even-odd asymmetry remains unclear,we propose that the coupling strength between electrons within the same Landau level and between the neighboring two Landau levels should be considered in future studies.The tilt field data show that the in-plane field can suppress the formation of both bubble and stripe phases.展开更多
^(75)As nuclear magnetic resonance(NMR)was measured for Ba(Fe_(1-x)Ni_(x))_(2)As_(2)single crystals with x=0.05 and x=0.1 under 0 and 1.5GPa,respectively.For the optimal doped sample with x=0.05,the superconducting tr...^(75)As nuclear magnetic resonance(NMR)was measured for Ba(Fe_(1-x)Ni_(x))_(2)As_(2)single crystals with x=0.05 and x=0.1 under 0 and 1.5GPa,respectively.For the optimal doped sample with x=0.05,the superconducting transition temperature,Tc,is strongly suppressed from 18 to 5 K,while for the over-doped sample with x=0.1,it is turned from a superconducting ground state to a disordered paramagnetic state under 1.5 GPa.Our experimental results show that the antiferromagnetic spin fluctuations,as well as Tc,are suppressed.The experimental results can be explained with the two-band model.As a result,the electronic band is shifted downwards with an increase in pressure,and the electrons become the dominant carriers in the system.展开更多
Periodic resistance oscillations in Fabry-Perot quantum Hall interferometers are observed at integer filling factors of the constrictions, f_c = 1, 2, 3, 4, 5 and 6. Rather than the Aharonov-Bohm interference, these o...Periodic resistance oscillations in Fabry-Perot quantum Hall interferometers are observed at integer filling factors of the constrictions, f_c = 1, 2, 3, 4, 5 and 6. Rather than the Aharonov-Bohm interference, these oscillations are attributed to the Coulomb interactions between interfering edge states and localized states in the central island of an interferometer, as confirmed by the observation of a positive slope for the lines of constant oscillation phase in the image plot of resistance in the B-Vs plane. Similar resistance oscillations are also observed when the area A of the center regime and the backscattering probability of interfering edge states are varied, by changing the side-gate voltages and the configuration of the quantum point contacts, respectively. The oscillation amplitudes decay exponentially with temperature in the range of 40 mK< T≤130 mK, with a characteristic temperature T_0~25 mK, consistent with recent theoretical and experimental works.展开更多
文摘Bi-based 2223 superconducting tapes with high critical current densities were prepared by silver-sheathingmethod.The relationship between processing,microstructure and property was discussed.The results of criti-cal current density measurement at 77.7 K with different applied magnetic field are as follows:j_e=2.87×10~4A/cm^2(OT),J_e=4100 A/cm^2(H I.H||S.1T)and J_e-B characteristics are obviously improved withtemperature decreasing from 77 K to 4.2 K.Microstructtlre observations indicate that intermediate pressingwith subsequent heat-trcating could lower the porosity of superconductor inside the silver sheath,and reducethe amount and size of non-superconducting phases,leading phases,leading to the formation of a strong c-axis-orientedtexture,and the emergence of high dislocation density within the 2223 grains,and consequently the J(?)andJ_e-B characteritics were improved.
基金Supported by the National Basic Research Program of China under Grant Nos 2015CB921101 and 2014CB920904the Strategic Priority Research Program B of Chinese Academy of Sciences under Grant No XDB07010200
文摘Triangular antidot lattices of various periods and aspect ratios are fabricated on high mobility GaAs/AlGaAs two-dimensional electron systems(2DESs),and are characterized by magneto-transport measurements at low temperatures down to 300 mK. Commensurability peaks are generally observed in the magneto-resistivity ρ_(xx),and remarkable similarity between dρ_(xy)/dB and ρ_(xx) is found. In samples of relatively large aspect ratio d/a, the Aharonov-Bohm-type oscillations are clearly observed in both ρ_(xx) and ρ_(xy), as well as the quenching of the Hall resistivity ρ_(xy) in the vicinity of B = 0. These observations evince the good quality of our samples, and attest to the adequate preparation for fabricating antidot lattices of a reduced period to realize artificial graphene from GaAs/AlGaAs 2DESs.
基金Supported by the National Basic Research Program of China under Grant Nos 2014CB920904 and 2015CB921101the Strategic Priority Research Program B of the Chinese Academy of Sciences under Grant No XDB07010200the Singapore National Research Foundation under Grant No NRF-RF2013-08
文摘Electronic transports of few-layer 1T'-MoTe_2 films are measured at temperatures down to 0.26 K. The lowtemperature conductivity exhibits logarithmic temperature dependence and negative magneto response. The negative magnetoconductivity can be well fitted by the two-dimensional weak anti-localization theory taking a single channel of electrons into account, with the parameters α≈-0.5 and l_φ∝ T^(-0 5). The logarithmic temperature dependence has a positive slope κ≈0.75, indicating the dominance of electron-electron interaction over the weak anti-localization effect, with an apparently negative Coulomb screening factor F that demands future work for clarification.
基金Project supported by the National Basic Research Program of China(Grant Nos.2016YFA0300601,2015CB921402,2011CB921702,and 2009CB929101)the National Natural Science Foundation of China(Grant Nos.11527806,91221203,11174340,11174357,and 91421303)+1 种基金the Strategic Priority Research Program B of the Chinese Academy of Sciences(Grant No.XDB07010100)the support from Hundreds Talent Program,Chinese Academy of Sciences
文摘The Institute of Physics, Chinese Academy of Sciences, is in charge of the construction of the Synergetic Extreme Condition User Facility(SECUF) in Huairou, Beijing. The SECUF is a comprehensive facility focused on providing extreme physical conditions for scientific research, including an ultralow temperature, ultrahigh pressure, ultrahigh magnetic field, and ultrafast laser. The ultralow temperature will be realized by the sub-millikelvin(sub-mK) station, whose main component is an adiabatic nuclear demagnetization refrigerator(ANDR). The refrigerator is designed to have a base temperature below 1 mK and a magnetic field up to 16 T for experiments, as well as a characteristic parameter of B/T≥10~4 T/K.In this review, we introduce adiabatic nuclear demagnetization refrigeration, thermometry from 10 mK to sub-mK, the properties and parameters of the ANDR of the SECUF, and related prospective research topics.
文摘There is no consensus whether the electron density of states of decagonal quasicrystals has a pseudogap at the Fermi energy similar to that of the icosahedron phase. We answer this question by measuring the electronic specific heat coefficient of AlCuCo decagonal single-quasicrystals over a wide range of composition. While the average valence electron number per atom, e/a, for all the resultant samples changes only within 1.5%, from-1.92 to less than 1.95. The specific heat coefficient decreases by 15% with the increasing e/a. The large change and the negative slope give strong evidence for Hume-Rothery mechanism of the decagonal phase.
基金Project supported by the National Basic Research Program of China(Grant Nos.2009CB929101 and 2011CB921702)the National Natural Science Foundation of China(Grant Nos.91221203,11174340,11174357,91421303,and 11527806)the Strategic Priority Research Program B of the Chinese Academy of Sciences(Grant No.XDB07010100)
文摘Full gap closing is a prerequisite for hosting Majorana zero modes in Josephson junctions on the surface of topological insulators.Previously,we have observed direct experimental evidence of gap closing in Josephson junctions constructed on Bi_2Te_3 surface.In this paper we report further investigations on the position dependence of gap closing as a function of magnetic flux in single Josephson junctions constructed on Bi_2Te_3 surface.
基金Supported by the National Basic Research Program of China under Grant Nos 2015CB921101 and 2016YFA0300600the National Natural Science Foundation of China under Grant No 11874406+2 种基金the Singapore National Research Foundation under Grant No NRF-NRFF2013-08the Tier 2 MOE2016-T2-2-153the A*Star QTE Programme
文摘We report on magnetoresistance, Hall effect, and quantum Shubnikov–de Haas oscillation(SdH) experiments in NbIrTe4 single crystals, which was recently predicted to be a type-II Weyl semimetal. NbIrTe4 manifests a non-saturating and parabolic magnetoresistance at low temperatures. The magneto-transport measurements show that NbIrTe4 is a multiband system. The analysis of the SdH oscillations reveals four distinct oscillation frequencies. Combined with the density-functional theory calculations, we show that they come from two types of Fermi surfaces: electron pocket E1 and hole pocket H2.
基金Supported by the National Basic Research Program of China under Grant Nos 2014CB920904 and 2013CB921702the National Natural Science Foundation of China under Grant Nos 11174340,11174357,91221203 and 91421303+2 种基金the Strategic Priority Research Program B of the Chinese Academy of Sciences under Grant No XDB07010100the Gordon and Betty Moore Foundation through the EPiQS initiative under Grant No GBMF4420the National Science Foundation of MRSEC under Grant No DMR-1420541
文摘Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells.The low-temperature longitudinal resistivity(ρ_(xx))data demonstrate that a striking even-odd asymmetric transport exists along the [110] direction at half filling in N > 2 high Landau levels.Although the origin for the peculiar even-odd asymmetry remains unclear,we propose that the coupling strength between electrons within the same Landau level and between the neighboring two Landau levels should be considered in future studies.The tilt field data show that the in-plane field can suppress the formation of both bubble and stripe phases.
基金Supported by the National Basic Research Program of China under Grant No 2011CB921701the National Natural Science Foundation of China under Grant No 11015422the Knowledge Innovation Program of the Chinese Academy of Sciences under Grant No KJCX2-EW-W11.
文摘^(75)As nuclear magnetic resonance(NMR)was measured for Ba(Fe_(1-x)Ni_(x))_(2)As_(2)single crystals with x=0.05 and x=0.1 under 0 and 1.5GPa,respectively.For the optimal doped sample with x=0.05,the superconducting transition temperature,Tc,is strongly suppressed from 18 to 5 K,while for the over-doped sample with x=0.1,it is turned from a superconducting ground state to a disordered paramagnetic state under 1.5 GPa.Our experimental results show that the antiferromagnetic spin fluctuations,as well as Tc,are suppressed.The experimental results can be explained with the two-band model.As a result,the electronic band is shifted downwards with an increase in pressure,and the electrons become the dominant carriers in the system.
基金Supported by the National Basic Research Program of China under Grant No 2014CB920904the National Natural Science Foundation of China under Grant No 91221203the Strategic Priority Research Program B of the Chinese Academy of Sciences under Grant No XDB07010200
文摘Periodic resistance oscillations in Fabry-Perot quantum Hall interferometers are observed at integer filling factors of the constrictions, f_c = 1, 2, 3, 4, 5 and 6. Rather than the Aharonov-Bohm interference, these oscillations are attributed to the Coulomb interactions between interfering edge states and localized states in the central island of an interferometer, as confirmed by the observation of a positive slope for the lines of constant oscillation phase in the image plot of resistance in the B-Vs plane. Similar resistance oscillations are also observed when the area A of the center regime and the backscattering probability of interfering edge states are varied, by changing the side-gate voltages and the configuration of the quantum point contacts, respectively. The oscillation amplitudes decay exponentially with temperature in the range of 40 mK< T≤130 mK, with a characteristic temperature T_0~25 mK, consistent with recent theoretical and experimental works.
