外磁场对THz波段超导表面等离激元的影响

Effects of external magnetic field on THz frequency surface plasmon polaritions at the superconductor surface

根据超导二流体模型,研究了在THz波段超导材料铌表面存在的表面等离激元的色散曲线和特征长度随外磁场的变化关系,分析了外磁场对表面等离激元激发条件的影响.结果表明:外磁场强度增大时,色散曲线偏离光锥线程度将增大,表面等离激元传播距离、归一化波长及其在介质内的穿透深度将变小,而在超导材料内的穿透深度将增大,且色散曲线和特征长度随磁场的变化程度还与频率有关.同时,共振角度对外磁场变化不敏感,但共振频率将随外磁场强度增大而红移.该结果可为超导波导器件设计提供一定的参考.

The dispersion relations and characteristics lengths of surface plasmon polaritions （SPPs） at the superconductor-air interface in THz band with different external magnetic fields are analyzed based on the two-fluid model, the changes of excitation frequency and angle in different external magnetic fields by attenuated total reflection （ATR） technique are also discussed. The results show that as the external magnetic field increases, the deviation degree of dispersion curve from light line is increased, and the SPPs propagation length, SPPs normalized wavelength and the penetration depth into air are de- creased, but the penetration depth into superconductor is increased. Moreover, the dispersion relations and characteristics lengths also vary with different frequencies. The excitation resonance angle is not sensitive to external magnetic field, but the resonance frequency increases with the increase of the exter- nal magnetic field. The changes of SPPs properties are ascribed to the electric state transformation be- tween superconducting and normal states.