Tunable bifunctional metamaterial terahertz absorber based on Dirac semimetal and vanadium dioxide

We propose herein a tunable bifunctional metamaterial terahertz absorber based on vanadium dioxide and a Dirac semimetal film. Given the phase-transition characteristics of vanadium dioxide, the proposed absorber can be switched between single- and dual-band absorption functions. In addition, the state of the proposed absorber can also switch between reflection (with a reflectance of 89% and 90.5% at 2.06 and 3.21 THz, respectively) and absorption (with an absorptance of 99.9% at 2.06 and 3.21 THz). Furthermore, we can dynamically tune the operating frequency of the proposed absorber by varying the Fermi energy of the Dirac semimetal film. The numerical results reveal that the proposed absorber is polarization-independent and maintains high absorptance over a broad range of angles of incidence. These results should help guide the design of tunable bifunctional metamaterial absorbers.