Tunable broadband-negative-permeability metamaterials by hybridization at THz frequencies

We present a numerical study of thermo-tunable broadband-negative-permeability metamaterial based on second-order hybridization operating at the THz regime. The conventional metal is replaced by InSb, in which the temperature-dependent conductivity plays a key role in tuning the separation of second-order-hybridization magnetic-resonance modes. It is demonstrated that the hybridization in a simple disk-pair dimer can be tuned by temperature, leading to a significant broadening of the negative-permeability at THz frequencies. By increasing the temperature of the InSb patterns in the structure from 300 to 450 K, the fractional bandwidth (FBW) of the negative permeability curve varies from 4.4% to 12.9%. The thermally-increased carrier-density of InSb reduces the kinetic inductance, the main mechanism of the enhanced magnetic-resonance and the stronger activated-hybridization. Moreover, optimization for the bandwidth of negative permeability is also carried out by changing the geometrical parameters to have a FBW of 20.9%. The equivalent LC-circuit model and standard retrieval method are performed to elaborate our proposed idea. Our results would pave the way for the implementations of diversified semiconductors in tunable broadband-negative-permeability and broadband-negative-refractive-index metamaterials at THz frequencies.