Showing papers by "Zhifeng Ren published in 1997"
TL;DR: In this article, the authors show that the single-layer tetragonal superconductor Tl2Ba2CuO6+δ has pure pairing symmetry, providing a starting point for understanding the more complex mixed s + d state that appears to characterize other high-temperature superconductors.
Abstract: Crucial to the successful development of a theoretical model for high-temperature superconductivity is knowledge of the symmetry of the order parameter (or wavefunction) that describes the pairing of electrons in the superconducting state. Several experimental studies1–8provide convincing evidence for an anisotropic order parameter, consistent with a symmetry. But none of these earlier experiments could rule out unambiguously an additional contribution from isotropic s-wave pairing; these experiments either involved superconductors with an orthorhombic crystal structure (for which a mixed s + d state is becoming increasingly recognized as a likely consequence9,10), or their interpretation required detailed modelling of the uncertain effects of disorder and defects. Here we report the results of an experiment designed to circumvent these difficulties: the material studied is the single-layer tetragonal superconductor Tl2Ba2CuO6+δ, and the experimental configuration is such that the interpretation of the results relies solely on symmetry considerations. Our results indicate that this material has pure pairing symmetry, so providing a starting point for understanding the more complex mixed s + d state that appears to characterize other high-temperature superconductors.
99 citations
TL;DR: In this paper, columnar vortex-pinning defects were formed by irradiation with 0.8 GeV protons, which led to significant enhancements in the current-conducting properties.
Abstract: In several Tl- and Hg-based high-Tc superconducting materials, vortex-pinning defects were formed by irradiation with 0.8 GeV protons. The protons cause heavy constituent nuclei (Tl, Hg, Bi, …) to fission, which generates randomly oriented tracks. These columnar defects lead to significant enhancements in the current-conducting properties. We investigated bulk materials and thin films, irradiated with or without Pb or Au “amplifier foil” overlayers, which increase the number of column-creating fission fragments.
23 citations
TL;DR: In this paper, the in-plane torque anisotropy of the high-T c cuprate Tl 2 Ba 2 CuO 6+δ gives evidence of a mixed s + d pairing state allowed by the possible breaking of its tetragonal symmetry at low temperature.
Abstract: The in-plane torque anisotropy of the high- T c cuprate Tl 2 Ba 2 CuO 6+δ gives evidence of a mixed s + d pairing state allowed by the possible breaking of its tetragonal symmetry at low temperature. The validity of our result is supported by the absence of any in-plane anisotropy in the classical superconductors NbN and the layered 2H-NbSe 2 measured under the same conditions.
3 citations