A bi-tunable polarization-independent triple-band metamaterial terahertz absorber with high refractive index sensitivity based on vanadium dioxide and bulk Dirac semimetal

We have proposed a novel terahertz metamaterial absorber based on the combination of vanadium dioxide and Dirac semimetal, which can be dual-controlled by adjusting the conductivity of vanadium dioxide or the Fermi energy of Dirac semimetal. The absorber achieves perfect absorption of 98.9%, 99.5%, and 98.5% at three operating frequencies of 1.504, 2.29, and 3.28 THz, respectively, when the conductivity of vanadium dioxide is set at 200,000 S/m, and the Fermi level of Dirac semimetal is set at 100 meV. Moreover, with vanadium dioxide's unique phase transition characteristics, absorptance switching from 9.6% to 98.9%, 14.1%-99.5%, and 9.9%- 98.5% can be achieved at three absorption peaks, respectively. Furthermore, the absorber is independent of polarization angles and can maintain an absorptance of over 92% at incident angles below 50 degrees, highlighting its significant potential for practical applications. Additionally, the absorber demonstrates remarkably high refractive index sensitivity, exhibiting 84, 160, and 294 GHz/RIU sensitivities at three peaks. This underscores its significance for applications in biochemical sensing and specialized environmental detection.