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[PAST EVENT] Colloquium - Vera Smolyaninova (Towson University)
October 30, 2015
4pm - 5pm
Abstract:
Superconducting properties of a material, such as electron-electron interactions and the critical temperature of superconducting transition may be expressed via the effective dielectric response function of the material. Such a description is valid on the spatial scales below the superconducting coherence length (the size of the Cooper pair), which equals ~100 nm in a typical BCS superconductor. Searching for natural materials exhibiting larger electron-electron interactions constitutes a traditional approach to high temperature superconductivity research. Recently developed field of electromagnetic metamaterials deals with somewhat related task of dielectric response engineering on sub-100 nm scale. The metamaterial approach to dielectric response engineering may considerably increase the critical temperature of a composite superconductor-dielectric metamaterial. Moreover, this approach has been verified in experiments with compressed mixtures of tin and barium titanate nanoparticles of varying composition and in experiments with core-shell aluminium-aluminum oxide metamaterials. We have demonstrated that Al2O3-coated aluminium nanoparticles may form the recently proposed epsilon near zero (ENZ) core-shell metamaterial superconductor with a TC that is three times that of pure aluminium. IR reflectivity measurements confirm the predicted metamaterial modification of the dielectric function thus demonstrating the efficacy of the ENZ metamaterial approach to TC engineering. These results open up numerous new possibilities of considerable TC increase in other simple superconductors.
Superconducting properties of a material, such as electron-electron interactions and the critical temperature of superconducting transition may be expressed via the effective dielectric response function of the material. Such a description is valid on the spatial scales below the superconducting coherence length (the size of the Cooper pair), which equals ~100 nm in a typical BCS superconductor. Searching for natural materials exhibiting larger electron-electron interactions constitutes a traditional approach to high temperature superconductivity research. Recently developed field of electromagnetic metamaterials deals with somewhat related task of dielectric response engineering on sub-100 nm scale. The metamaterial approach to dielectric response engineering may considerably increase the critical temperature of a composite superconductor-dielectric metamaterial. Moreover, this approach has been verified in experiments with compressed mixtures of tin and barium titanate nanoparticles of varying composition and in experiments with core-shell aluminium-aluminum oxide metamaterials. We have demonstrated that Al2O3-coated aluminium nanoparticles may form the recently proposed epsilon near zero (ENZ) core-shell metamaterial superconductor with a TC that is three times that of pure aluminium. IR reflectivity measurements confirm the predicted metamaterial modification of the dielectric function thus demonstrating the efficacy of the ENZ metamaterial approach to TC engineering. These results open up numerous new possibilities of considerable TC increase in other simple superconductors.