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《Solid State Communications》1987,64(4):421-424
When La in body-centered-tetragonal La2CuO4 is substituted by Ba only tetragonal symmetry remains with two formula units per unit cell. Assuming an ordered La3BaCu2O8 structure the effect of substitution on the energy bands is studied by electronic-structure calculations employing the augmented-spherical-wave (ASW) method. It is found that Cu-d O-p interactions not only in the xy plane are important, but also in the z direction when oxygen atoms are involved which are near Ba. The stabilizing electrostatic effect of Ba2+ ions is reduced in comparison to La3+ ions and cause the oxygen states near Ba2+ to be raised in energy. This mechanism effectively reduces the coordination of Cu to essentially fivefold (as found in YBa2Cu3O7. The two inequivalent Cu atoms differ such that the symmetry breaking could support valence fluctuations. 相似文献
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The ab-plane optical properties of a cleaved single crystal of La2-xBaxCuO4 for x=1/8 (Tc approximately =2.4 K) have been measured over a wide frequency and temperature range. The low-frequency conductivity is Drude-like and shows a metallic response with decreasing temperature. However, below approximately =60 K, corresponding to the onset of charge-stripe order, there is a rapid loss of spectral weight below about 40 meV. The behavior is quite different from that typically associated with the pseudogap in the normal state of the cuprates. Instead, the gapping of the normal-state single-particle excitations looks surprisingly similar to that observed in superconducting La2-xSrxCuO4, including the presence of a residual Drude peak with reduced weight. 相似文献
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本文报道了在室温下对La2-xBaxCuO4超导系列样品的正电子寿命谱(PAT)测量,讨论了正电子湮没机制与超导转变温度的关联,并从电子密度转移方面解释了La2-xBaxCuO4超导样品在1/8处的转变温度受抑制的原因. 相似文献
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本文报道了在室温下对La2-xBaxCuO4超导系列样品的正电子寿命谱(PAT)测量,讨论了正电子湮没机制与超导转变温度的关联,并从电子密度转移方面解释了La2-xBaxCuO4超导样品在1/8处的转变温度受抑制的原因. 相似文献
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The report that T(c) was doubled in underdoped La2-xSrxCuO4 films under compressive epitaxial strain has stirred great interest. We show that such films are extremely sensitive to oxygen intake, even at very low temperature, with startling consequences including colossal lattice expansion and a crossover from semiconductor to metallic behavior. We can bring T(c) up to 40 K in La2CuO4 films on SrTiO3 substrates-without any Sr doping and under tensile strain. On LaSrAlO4 substrates, we reached T(c)=51.5 K, the highest so far in La2-xSrxCuO4. 相似文献
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《Physics letters. A》1988,132(5):290-292
It is possible to induce excess charge on the surface of dielectric La2CuO4 by the field effect of a transistor or in the Schottky junction. Superconductivity can be observed in this two-dimensional system. 相似文献
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We investigate the dynamics of the Josephson vortex lattice in layered high- T(c) superconductors at high magnetic fields. It is shown that the average electric current depends on the lattice structure and is resonantly enhanced when the Josephson frequency matches the frequency of the plasma mode. We find the stability regions of a moving lattice. It is shown that a specific lattice structure at a given velocity is uniquely selected by the boundary conditions; at small velocities a periodic triangular lattice is stable and looses its stability at some critical velocity. At even higher velocities, a structure close to a rectangular lattice is restored. 相似文献