X. X. Xi

Publications (3)2.66 Total impact

• Source

  Available from: ArXiv

  Article: Influence of intrinsic electronic properties on light transmission through subwavelength holes on gold and MgB_ {2} thin films

  Xu Fang, Chenggang Zhuang, Zhenchao Wen, Xiufeng Han, Qingrong Feng, X. X. Xi, Franco Nori, Xincheng Xie, Qian Niu, Xianggang Qiu
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  ABSTRACT: We show how intrinsic material properties modify light transmission through subwavelength hole arrays on thin metallic films in the THz regime. We compare the temperature-dependent transmittance of Au films and MgB2 films. The experimental data are consistent with analytical calculations and are attributed to the temperature change of the conductivity of both films. The transmission versus conductivity is interpreted within the open resonator model when taking the skin depth into consideration. We also show that the efficiency of this temperature control depends on the ratio of the transmission peak frequency to the superconducting energy gap in MgB2 films.
  Phys. Rev. B. 11/2011; 84(20).
• Article: Clean MgB2 thin films on different types of single-crystal substrate fabricated by hybrid physical–chemical vapor deposition

  Chenggang Zhuang, Teng Tan, Yazhou Wang, Shanshan Bai, Xiaobai Ma, Huan Yang, Guohua Zhang, Yusheng He, Haihu Wen, X X Xi, Qingrong Feng, Zizhao Gan
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  ABSTRACT: Phase pure and clean MgB2 films have been fabricated on different types of single-crystal substrate, including SiC, sapphire, MgO, LaAlO3, SrTiO3, and yttrium-stabilized ZrO2 (YSZ), via the hybrid physical–chemical vapor deposition (HPCVD) technique. Pure MgB2 films with different structural textures are obtained by selecting the substrate and its orientation, such as off-axis epitaxial MgB2 on MgO(211) or textured MgB2 on YSZ(110) substrates. Films show Tc(0) in the range 37–41 K, and residual resistivity ρ(42 K) between 0.3 and 5 µΩ cm as the substrate and film thickness are varied. The crystal structures and film morphologies are presented and discussed. Further investigations are focused on c-axis epitaxial films. Epitaxial MgB2 films with thickness about 300 nm manifest Tc(0) = 41.2 K and residual resistivity ρ(42 K) = 0.35 µΩ cm on SiC(0001) while Tc(0) = 39.5 K and ρ(42 K) = 0.27 µΩ cm on c-cut sapphire, reflecting that the films are of high quality and in the 'clean limit'. Low upper critical field and large anisotropy of the upper critical field γ comparable to the results from MgB2 single crystals are also revealed. The smooth surface of the epitaxial films, with root-mean-square (RMS) roughness less than 5 nm, makes them well qualified for device applications. Microwave performance measurements are carried out using a coplanar resonator on a 300 nm thick film on sapphire substrate and no power dependence of unloaded quality factor in the output power range of −10–25 dB is found.
  Superconductor Science and Technology 12/2008; 22(2):025002. · 2.66 Impact Factor
• Source

  Available from: ArXiv

  Article: Scaling of Hall Resistivity in the Mixed State of MgB2 Films

  Huan Yang, Ying Jia, Lei Shan, Chenggang Zhuang, X. X. Xi, Qi Li, Zikui Liu, Qingrong Feng, Hai-Hu Wen
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  ABSTRACT: The longitudinal resistivity (rho_{xx}) and transverse resistivity (rho_{xy}) of MgB2 thin films in the mixed state were studied in detail. We found that the temperature dependencies of rho_{xx} and \rho_{xy} at a fixed magnetic field (H) satisfy the scaling law of $\rho_{xy}=A\rho_{xx}^\beta$, where the exponent beta varies around 2.0 for different fields. In the low field region (below 1T), beta maintains a constant value of 2.0 due to the weak pinning strength of the vortices, mainly from the superfluid of the pi band. When H>1T, beta drops abruptly to its lowest value at about 2T because of the proliferation of quasiparticles from the pi-band and, hence, the motion of the vortices from the superfluid of the sigma-band dominates the dissipation. As the field is increased further, the vortex pinning strength is weakened and beta increases monotonically towards 2.0 at a high field. All the results presented here are in good agreement with the expectation of the vortex physics of a multi-band superconductor.
  02/2008;