摘要 :
Samples of Nd_(2-x)Ce_xCuO_4, an electron-doped high-temperature superconducting cuprate, near optimal doping at x=0.155 were measured via angle-resolved photoemission. We report a renormalization feature in the self-energy ("kink...
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Samples of Nd_(2-x)Ce_xCuO_4, an electron-doped high-temperature superconducting cuprate, near optimal doping at x=0.155 were measured via angle-resolved photoemission. We report a renormalization feature in the self-energy ("kink") in the band dispersion at ≈50-60 meV present in nodal and antinodal cuts across the Fermi surface. Specifically, while the kink had been seen in the antinodal region, it is now observed also in the nodal region, reminiscent of what has been observed in hole-doped cuprates.
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Single crystals of thallium-based cuprates with the general formula Tl_2Ba_2Ca_(n-1)Cu_nO_x (n=1,2,3) have been grown by the flux method. The superconducting transition temperatures determined by the ac magnetic susceptibility are...
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Single crystals of thallium-based cuprates with the general formula Tl_2Ba_2Ca_(n-1)Cu_nO_x (n=1,2,3) have been grown by the flux method. The superconducting transition temperatures determined by the ac magnetic susceptibility are 92, 109, and 119 K for n= 1,2,3, respectively. X-ray diffraction measurements and an EDX compositional analysis were described. We measured in-plane optical reflectance from room temperature down to 10 K, placing an emphasis on Tl-2223. The reflectance roughly has a linear-frequency dependence above the superconducting transition temperature, but displays a pronounced knee structure together with a diplike feature at higher frequency below T_c. Correspondingly, the ratio of the reflectances below and above T_c displays a maximum and a minimum near those feature frequencies. In particular, those features in Tl2223 appear at a higher-energy scale than Tl2212 and Tl2201. The optical data are analyzed in terms of the spectral function. We discussed the physical consequences of the data in terms of both clean and dirty limits.
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We report electrical resistivity on a single crystal of the hole-doped two-leg ladder compound Sr_2Ca_(12)Cu_(24)O_(41), which becomes superconducting with T_c ～ 5 K only at pressures above ～3.0 GPa. Measurements were performed ...
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We report electrical resistivity on a single crystal of the hole-doped two-leg ladder compound Sr_2Ca_(12)Cu_(24)O_(41), which becomes superconducting with T_c ～ 5 K only at pressures above ～3.0 GPa. Measurements were performed at nearly hydrostatic pressures up to 5.7 GPa and low temperatures down to 100 mK under static magnetic fields up to 20 T parallel to the a axis (along the ladder rungs) and up to 7 T parallel to both the b axis (perpendicular to the ladder plane) and the c axis (along the ladder legs). A clear difference in the resistive upper critical field H_(c2)(T) is observed among these three directions, confirming that this system has a highly anisotropic superconducting ground state. Also, H_(c2)(T) parallel to the ladder plane is found to exceed the Pauli limit by a factor of more than 2, suggesting either a strong spin-orbit scattering or spin-triplet pairing. Furthermore, it is implied, from measurements of resistivity versus angle of magnetic field in the bc plane, that another superconducting phase is stable below around 3 K only when the magnetic field is applied exactly along a certain direction that is ± 35° from the ladder direction.
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We report the reversible magnetization of the Ca_(2-x)Na_xCuO_2Cl_2 (x=0.18) single crystal for H‖c up to 1.2 T to study the effect of oxygen replacement by chlorine at the apical site. The superconducting transition temperature ...
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We report the reversible magnetization of the Ca_(2-x)Na_xCuO_2Cl_2 (x=0.18) single crystal for H‖c up to 1.2 T to study the effect of oxygen replacement by chlorine at the apical site. The superconducting transition temperature T_c (～27 K) of this single crystal is the highest reported in this family. Various thermodynamic parameters, such as the penetration depth λ_(ab)(0), the coherence length ξ_(ab)(0), the critical field H_c(0), the upper critical field H_(c2)(0) and the Ginzburg-Landau parameter κ, are also reported. Compared to the iso-structural compound La_(1.82)Sr_(0.18)CuO_4 with apical oxygen, Ca_(1.82)Na_(0.18)CuO_2Cl_2 has two significant differences: (1) λ_(ab)(0) is larger, so the Cooper pair density is quite reduced, and (2) the anisotropic nature is more enhanced. From these observations, chlorine at the apical site is thought to be less effective than oxygen in supplying charge carriers to the CuO_2 planes; as a result, the interlayer coupling between the CuO_2 planes is weakened.
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We have measured dissipation-induced localization of the reaction coordinate for a metastable-state decay process in a model system with moderate damping. Specifically, the supercurrent in an array of Tl_2Ba_2CaCu_2O_8 intrinsic J...
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We have measured dissipation-induced localization of the reaction coordinate for a metastable-state decay process in a model system with moderate damping. Specifically, the supercurrent in an array of Tl_2Ba_2CaCu_2O_8 intrinsic Josephson junctions is larger when all the junctions are in the zero-voltage state than when one or more junctions are in the voltage state since the dissipation is larger in the former case.
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摘要 :
Here we report the first angle-resolved photoemission measurement on nearly optimally doped multilayer Tl-based superconducting cuprates (Tl-2212 and Tl-1223) and a comparison study to single-layer (Tl-2201) compound. A "kink" in ...
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Here we report the first angle-resolved photoemission measurement on nearly optimally doped multilayer Tl-based superconducting cuprates (Tl-2212 and Tl-1223) and a comparison study to single-layer (Tl-2201) compound. A "kink" in the band dispersion is found in all three compounds but exhibits different momentum dependence for the single-layer and multilayer compounds, reminiscent to that of Bi-based cuprates. This layer number dependent renormalization effect strongly implies that the spin-resonance mode is unlikely to be responsible for the dramatic renormalization effect near the antinodal region.
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The detection of quantum oscillations in the electrical resistivity of YBa_2Cu_3O_(6.5) provides evidence for the existence of Fermi-surface pockets in an underdoped cuprate. We present a theoretical study of the electronic struct...
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The detection of quantum oscillations in the electrical resistivity of YBa_2Cu_3O_(6.5) provides evidence for the existence of Fermi-surface pockets in an underdoped cuprate. We present a theoretical study of the electronic structure of YBa_2Cu_3O_(7-δ) a
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We report on magnetic investigation on PrBa_2Cu_3O_(6+x) compounds (0.4 < x < 1.0) where the Pr_(3+) ions exhibit an antiferromagnetic order (AF) at T_N ～11 K for x ～ 0.5 and 17 K for x ～ 1. For better understanding of the role of the praseodymium and oxygen content on magnetic and transport properties, we measured temperature and field dependence of susceptibility and magnetization of PrBa_2Cu_3O_(6+x) in two oxygenation states x = 0.4 and 0.9. We show that a careful analysis of these data can bring to evidence the existence of several tiny transitions, especially a sharp one around 13 K which may be related to a change of direction of copper moments....
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We report on magnetic investigation on PrBa_2Cu_3O_(6+x) compounds (0.4 < x < 1.0) where the Pr_(3+) ions exhibit an antiferromagnetic order (AF) at T_N ～11 K for x ～ 0.5 and 17 K for x ～ 1. For better understanding of the role of the praseodymium and oxygen content on magnetic and transport properties, we measured temperature and field dependence of susceptibility and magnetization of PrBa_2Cu_3O_(6+x) in two oxygenation states x = 0.4 and 0.9. We show that a careful analysis of these data can bring to evidence the existence of several tiny transitions, especially a sharp one around 13 K which may be related to a change of direction of copper moments.
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摘要 :
Studies of magnetic and transport properties of the 1212 compounds MA_2′A″Cu_2O_(7-x) (M = Al or Tl; A′ = Sr or Ba; A″= RE, Y, and Ca) revealed a number of interesting magnetic phenomena. Apart from high-temperature supercondu...
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Studies of magnetic and transport properties of the 1212 compounds MA_2′A″Cu_2O_(7-x) (M = Al or Tl; A′ = Sr or Ba; A″= RE, Y, and Ca) revealed a number of interesting magnetic phenomena. Apart from high-temperature superconductivity, these compounds exhibit spontaneous antiferromag-netism, field induced antiferromagnetism or ferromagnetism. The different magnetic orders and superconductivity may be realized in the same compound as a result of the phase separation.
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We present a detailed positron 2D-ACAR measurements study of the "ridge" Fermi surface of (R)Ba_2Cu_3O_(7-δ) (R = Y, Dy) compared to full-potential linearized augmented plane wave and linear muffin-tin orbital calculations. From ...
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We present a detailed positron 2D-ACAR measurements study of the "ridge" Fermi surface of (R)Ba_2Cu_3O_(7-δ) (R = Y, Dy) compared to full-potential linearized augmented plane wave and linear muffin-tin orbital calculations. From different 2D-ACAR projections measured in DyBa_2Cu_3O_(7-δ), a 3D model of the momentum density of the ridge was established and is in good agreement with LMTO calculations of YBa_2Cu_3O_7, confirming the description of the ridge Fermi surface by local density approximation calculations. The ridge is also studied in oxygen deficient YBa_2Cu_3O_(7-δ). With growing δ, the ridge disappears without changing in width. This is consistent with full-potential linearized augmented plane wave calculations of YBa_2Cu_3O_(6.5), and supports the phase separation model of Mesot et al.
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