We have studied flux line confinement by regular arrays of submicron holes (triangular and square antidot lattices) in superconducting films. Critical current density j c and pinning force f p are very strongly enhanced due to pinning of single or multi-quanta vortices by the antidots. Direct measurements of j c and f p for several well-defined antidot diameters D, proves that pinning centers with size considerably larger than the temperature-dependent coherence length ξ(T) are much more efficient than those with D\congξ(T).
A new class of media with abnormal electromagnetic parameters has been attracting increasing attention because of its exotic properties and potential application. Currently, typical metamaterials are mainly composed of artificially designed metallic periodic structures. However, due to the limitations of available fabrication technologies, physical size and material effects, it is difficult to realize these abnormal properties by these artificial structures in the high-frequency regime. Therefore, it is important to find materials with intrinsic abnormal electromagnetic responses. In this field, a new mechanism based on the interaction between polar lattice vibrations and electromagnetic waves has been proposed. In this paper, we review progress in this field. abnormal electromagnetic medium, polar lattice vibration, intrinsic property, infrared, indefinite medium Citation:Wang R, Zhou J, Qiu X G. Intrinsic abnormal electromagnetic medium based on polar lattice vibration. Chinese Sci Bull, 2011Bull, , 56: 1318Bull, −1324Bull, , doi: 10.1007 Abnormal electromagnetic (EM) medium refer to a kind of material system with abnormal permittivity and permeability (negative or less than unity), which is typically represented by left handed material (LHM) with negative permittivity and permeability at the same time. Abnormal EM medium is normally realized via metamaterials based on metallic periodic structures [1][2][3][4][5][6][7][8][9][10][11][12]. The abnormal properties in the metamaterial usually originate from the artificial structure, and not from the materials themselves. These materials attracted much attention not only because of their scientific significance, but also their potential for enlargement of the performance scale, and design of new functional materials. Conventional metamaterials are based on highly engineered artificial structure units, normally with electric or magnetic resonances, such as wires and split ring resonators (SRRs) [2,[4][5][6][7][8][9]. In the infrared and optical regions, metamaterials are showing more and more shortcomings for the current fabrication technologies, characteristic physical size and material effects of metals in mesoscopic scale. However, intrinsic EM responses in nature existed materials provide another choice. For example, ferromagnetic resonances in ferrites can provide tunable negative permeability at microwave frequency [16][17][18], and the electric resonance in ferroelectric can be used to achieve a negative permittivity [19,20]. However, because of their high frequency cutoffs, these EM resonances cannot be extended to the infrared or optical regions, restricting the development of intrinsic abnormal media. Therefore, it is a challenging problem to realize intrinsic abnormal EM properties in the high frequency regime. Recently, abnormal EM media based on polar lattice vibrations in the infrared region have attracted
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