Fig. 1. (a) The electronic dispersion of graphene. (b) Calculated band structures of bulk MoS₂ and monolayer MoS₂. The arrows indicate the indirect and direct bandgaps, respectively. (a) Reproduced with permission from Ref. [59]. Copyright 2009, APS. (b) Reproduced with permission from Ref. [50]. Copyright 2011, APS.

Fig. 2. (a) Schematics of the metasurface with the graphene transferred onto the array of Al mesas. (b) Phase modulation performance measured at different frequencies and gate biases. (c) The phase difference between waves at different polarizations. (d) Representation of coupled resonator structure. (e) The simulated transmission through the resonator as a function of frequency at different values of graphene conductivity. (a)–(c) Reproduced with permission from Ref. [73]. Copyright 2015, APS. (d), (e) Reproduced with permission from Ref. [76]. Copyright 2018, Wiley-VCH.

Fig. 3. (a) Illustration of a tunable metasurface consisting of graphene ribbons on a Ag mirror with a SiO₂ gap layer. (b) Simulation result of reflectance spectra at different Fermi levels for the TM polarization. (c) 3D schematic representation of the complementary split-ring resonators-graphene hybrid metasurface on a SiO₂/Si substrate. (d) The transmission modulation of the device operating at 4.5 THz. (a), (b) Reproduced with permission from Ref. [86]. Copyright 2015, AIP. (c), (d) Reproduced with permission from Ref. [94]. Copyright 2015, Springer Nature.

Fig. 4. (a) Schematic of multilayer MoS₂ dropped casted on asymmetric resonator under the illumination of the optical pump and THz probe pulses. The inset shows the cross-section of the unit cell. (b) Measured terahertz transmission spectra without MoS₂ and with MoS₂ at different optical pump fluences. (c) Schematic of WSe₂ covered metasurface. (d) Power dependence of the THz transmission at different pump fluences. (e) Transient evolution of the ultrafast THz switching metasurface. (a), (b) Reproduced with permission from Ref. [96]. Copyright 2017, Wiley-VCH. (c)–(e) Reproduced with permission from Ref. [97]. Copyright 2020, Elsevier.

Fig. 5. (a) HRTEM image of monoclinic/rutile domain walls in VO₂ and in situ domain wall motion observation of monoclinic VO₂ at 25 °C, 50 °C, and 70 °C. (b) Quantum well structure with a sandwich VO₂ layer. (c) Capacitance changes with the dc voltage at 25 °C. Inset shows the capacitance,-voltage curve at 80 °C. (a) Reproduced with permission from Ref. [101], copyright 2014, Springer Nature. (b), (c) Reproduced with permission from Ref. [103], copyright 2015, AIP.

Fig. 6. (a) Schematic energy diagram for THz-driven IMT in VO₂ and resistivity hysteresis curves. (b) Illustration of the THz-pump/x-ray probe experiment and the relevant observable processes. (a) Reproduced with permission from Ref. [108], copyright 2015, ACS. (b) Reproduced with permission from Ref. [109], copyright 2018, APS.

Fig. 7. (a) Illustrations of metasurface with metal resonator patterns on a VO₂ film and the transmission spectra at different temperatures. (b) Diagram of the VO₂ based hybrid metasurface and the transmission spectra at different values of electric current. (c) The sketch of the metasurface and phase spectra with the increasing light power. (a) Reproduced with permission from Ref. [33], copyright 2010, ACS. (b) Reproduced with permission from Ref. [124], copyright 2018, Wiley-VCH. (c) Reproduced with permission from Ref. [123], copyright 2018, ACS.

Fig. 8. (a) Electric field distribution in Lorentzian and Fano resonators for YBCO and aluminum, respectively, the optical image of the fabricated Fano resonator samples. (b) Measured amplitude transmission spectra. (a), (b) Reproduced with permission from Ref. [137], copyright 2017, AIP.

Fig. 9. (a) Measured transmission amplitude spectrum of the metasurface at different temperatures. (b) Planar geometry of NbN based metasurface. (c) THz transmission spectra at different temperatures. (d) Ultra-fast all-optical switch based on YBCO hybrid metasurface. (a) Reproduced with permission from Ref. [142], copyright 2010, APS. (b), (c) Reproduced with permission from Ref. [143], copyright 2011, AIP. (d) Reproduced with permission from Ref. [144], copyright 2018, Wiley-VCH.

Fig. 10. (a) Schematic of a superconducting NbN metasurface. (b) Effective surface reactance and resistance as a function of THz electrical field and (c) as a function of temperature. (d) The THz metasurface in which the light area is YBCO and the dark area is LaAlO₃ substrate. (e) THz field strength-dependent transmission spectra at different temperatures. (a)–(c) Reproduced with permission from Ref. [133], copyright 2013, AIP. (d), (e) Reproduced with permission from Ref. [146], copyright 2013, IOP.

Fig. 11. (a) Schematic structure of isolator based on the MO metasurface. (b) The transmission spectrum of the forward waves and backward waves at T = 195 K and B = 0.3 T, respectively. The inset shows the isolation spectra of the isolator. (c) The sketch of the hybrid metasurface composed of a monolayer graphene and gold array separated by SiO₂ layer. (a), (b) Reproduced with permission from Ref. [155], copyright 2015, OSA. (c) Reproduced with permission from Ref. [157], copyright 2018, OSA.