Fig. 1. Schematic of metasurface unit structure. (a) 3D model of metasurface unit structure; (b) top view of Dirac semimetallic layer; (c) top view of metasurface unit structure; (d) front view of unit structure

Fig. 2. Dynamic conductivity of Dirac semimetals at different Fermi energy levels. (a) Real part; (b) imaginary part

Fig. 3. Transmission spectra when vanadium dioxide is in the insulating state

Fig. 4. Transmission spectra of C1-MASRR, C2-MASRR, and MASRR when d=15 μm. (a) Transmission spectra at 0-1.3 THz; (b) transmission spectra at 1.3-2 THz

Fig. 5. Electric field distribution at transmission peaks p1 and p2. (a) Electric field diagram of C2-MSRR at p1; (b) electric field diagram of MASRR at p1; (c) electric field diagram of C1-MSRR at p1; (d) electric field diagram of C2-MSRR at p2; (e) electric field diagram of MASRR at p2; (f) electric field diagram of C1-MSRR at p2

Fig. 6. Electric field distribution at transmission peak p3. (a) d=0 μm; (b) d=5 μm; (c) d=10 μm; (d) d=15 μm

Fig. 7. Transmission spectra of asymmetric parameter d increasing from 0 μm to 15 μm

Fig. 8. Plots of Q variation corresponding to each resonance point as d increases from 0 μm to 15 μm. (a) Q variation with d for d1, p1, and p2; (b) Q variation with d for d3, p3, and d4

Fig. 9. Transmission spectra when the Fermi energy level (E_F) increases from 90 meV to 170 meV

Fig. 10. Schematic of the sample covering whole resonant structure (200 μm×100 μm). (a) 3D view; (b) front view

Fig. 11. Transmission spectra and resonance frequency shift as a function of refractive index. (a) Transmission spectra of resonance structure when refractive index n of covered sample is increased from 1 to 2; (b) fitting curve of frequency shift at the resonance point of d3 when refractive index n of covered sample increases from 1 to 2

Fig. 12. LC resonance model

Fig. 13. Variation of frequency shift with sample thickness. (a) Transmission spectra at d3 when increasing sample thickness t from 5 μm to 50 μm ; (b) variation of frequency shift of d3 with sample thickness t

Fig. 14. Variation curve of sensitivity at d3 with sample thickness t

Fig. 15. Variation of sensitivity with distance between sample and metasurface

Fig. 16. Transmission and reflection spectra of vanadium dioxide in the metallic state

Fig. 17. Transmission spectra of vanadium dioxide in the insulating and metallic states

Fig. 18. Electric field diagrams at p2 and p3. (a) Electric field at p2 when vanadium dioxide is in the insulating state; (b) electric field at p2 when vanadium dioxide is in the metallic state; (c) electric field at p3 when vanadium dioxide is in the insulating state; (d) electric field at p3 when vanadium dioxide is in the metallic state

Fig. 19. Electric field diagrams. (a) Electric field diagram at d1 when vanadium dioxide is in the insulating state; (b) electric field diagram at d1 when vanadium dioxide is in the metallic state; (c) electric field diagram at the center frequency of the filter when vanadium dioxide is in the insulating state; (d) electric field diagram at the center frequency of the filter when vanadium dioxide is in the metallic state

Fig. 20. Transmission spectra of vanadium dioxide in the metallic state with different asymmetric parameters

Fig. 21. Transmission spectra at different Fermi energy levels