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Tetsuo Hanaguri - One of the best experts on this subject based on the ideXlab platform.

  • Observation of structures of chain vortices inside anisotropic high- Tc superconductors.
    Physical review letters, 2002
    Co-Authors: Akira Tonomura, Kohji Kishio, T Yoshida, Osamu Kamimura, Hiroto Kasai, Tsuyoshi Matsuda, Ken Harada, Tetsuya Akashi, Jun-ichi Shimoyama, Tetsuo Hanaguri
    Abstract:

    In order to elucidate the formation mechanism of unconventional arrangements of vortices in high- Tc superconducting thin films at an inclined magnetic field to the Layer Plane, we investigated the structures of vortex lines inside the films by Lorentz microscopy using our 1-MV field-emission electron microscope. Our observation results concluded that vortex lines are tilted to form linear chains in YBaCu3O(7,8). Vortex lines in the chain-lattice state in Bi2Sr2CaCu2O(8+delta), on the other hand, are all perpendicular to the Layer Plane, and therefore only vortices lined up along Josephson vortices form chains.

Weitin Chen - One of the best experts on this subject based on the ideXlab platform.

  • negative thermal expansion in high pressure Layered perovskite ca2geo4
    Chemical Communications, 2019
    Co-Authors: Weitin Chen, Chris Ablitt, Nicholas C Bristowe, Arash A Mostofi, Takashi Saito, Yuichi Shimakawa, Mark S Senn
    Abstract:

    We report the high pressure synthesis of a Layered perovskite Ca2GeO4 which is found to have the Ruddlesden–Popper structure with I41/acd symmetry. Consonant with our recent predictions [Ablitt et al., npj Comput. Mater., 2017, 3, 44], the phase displays pronounced uniaxial negative thermal expansion over a large temperature range. Negative thermal expansion that persists over a large temperature range is very unusual in the perovskite structure, and its occurrence in this instance can be understood to arise due to both soft lattice vibrations associated with a phase competition and the unusually compliant nature of this structure, which effectively couples thermal expansion in the Layer Plane to lattice contractions perpendicular to the Layering direction via a “corkscrew” mechanism.

Mark S Senn - One of the best experts on this subject based on the ideXlab platform.

  • negative thermal expansion in high pressure Layered perovskite ca2geo4
    Chemical Communications, 2019
    Co-Authors: Weitin Chen, Chris Ablitt, Nicholas C Bristowe, Arash A Mostofi, Takashi Saito, Yuichi Shimakawa, Mark S Senn
    Abstract:

    We report the high pressure synthesis of a Layered perovskite Ca2GeO4 which is found to have the Ruddlesden–Popper structure with I41/acd symmetry. Consonant with our recent predictions [Ablitt et al., npj Comput. Mater., 2017, 3, 44], the phase displays pronounced uniaxial negative thermal expansion over a large temperature range. Negative thermal expansion that persists over a large temperature range is very unusual in the perovskite structure, and its occurrence in this instance can be understood to arise due to both soft lattice vibrations associated with a phase competition and the unusually compliant nature of this structure, which effectively couples thermal expansion in the Layer Plane to lattice contractions perpendicular to the Layering direction via a “corkscrew” mechanism.

Rudolf Zentel - One of the best experts on this subject based on the ideXlab platform.

  • Study of smectic elastomer films under uniaxial stress
    Liquid Crystals, 2004
    Co-Authors: Ralf Stannarius, R. Köhler, Martin Rössle, Rudolf Zentel
    Abstract:

    We study the mechanical properties of free-standing films of smectic liquid crystalline elastomers. Macroscopically ordered elastomer films of submicrometer thickness are prepared from freely suspended smectic A polymer films by photo crosslinking. The deformation characteristics depend criticically on the sample composition, in particular on the density of mesogenic side chains at the siloxane backbone. In materials where the siloxane backbone is only partially substituted (dilute systems), a uniaxial stretching of the films in the Layer Plane is accompanied by a shrinkage of the smectic Layers. This Layer shrinkage is to only a minor extent achieved by the induction of a molecular tilt. We conclude that the Layer compression modulus (enthalpic contribution to elasticity) in such materials is very weak. In materials with a fully substituted backbone (homopolymers), the smectic Layer thickness is preserved under uniaxial stress in the Layer Planes.

Kohji Kishio - One of the best experts on this subject based on the ideXlab platform.

  • Observation of structures of chain vortices inside anisotropic high- Tc superconductors.
    Physical review letters, 2002
    Co-Authors: Akira Tonomura, Kohji Kishio, T Yoshida, Osamu Kamimura, Hiroto Kasai, Tsuyoshi Matsuda, Ken Harada, Tetsuya Akashi, Jun-ichi Shimoyama, Tetsuo Hanaguri
    Abstract:

    In order to elucidate the formation mechanism of unconventional arrangements of vortices in high- Tc superconducting thin films at an inclined magnetic field to the Layer Plane, we investigated the structures of vortex lines inside the films by Lorentz microscopy using our 1-MV field-emission electron microscope. Our observation results concluded that vortex lines are tilted to form linear chains in YBaCu3O(7,8). Vortex lines in the chain-lattice state in Bi2Sr2CaCu2O(8+delta), on the other hand, are all perpendicular to the Layer Plane, and therefore only vortices lined up along Josephson vortices form chains.

  • Oscillating rows of vortices in superconductors
    Science, 2001
    Co-Authors: T. Matsuda, H. Kasai, J Shimoyama, Y. Nakayama, Akira Tonomura, T Yoshida, Osamu Kamimura, K. Harada, Teruhisa Akashi, Kohji Kishio
    Abstract:

    Superconductors can be used as dissipation-free electrical conductors as long as vortices are pinned. Vortices in high-temperature superconductors, however, behave anomalously, reflecting the anisotropic Layered structure, and can move readily, thus preventing their practical use. Specifically, in a magnetic field tilted toward the Layer Plane, a special vortex arrangement (chain-lattice state) is formed. Real-time observation of vortices using high-resolution Lorentz microscopy revealed that the images of chain vortices begin to disappear at a much lower temperature, Td, than the superconducting transition temperature, Tc. We attribute this image disappearance to the longitudinal oscillation of vortices along the chains.