Fig. 1

Tunable meta-atoms with transparent conducting oxides. a An ITO layer under external bias modulates the charge accumulation region near ENZ dispersion condition, resulting in a phase shift for the reflected light in the SWIR region [51]. Reproduced with permission from ©2016, American Chemical Society. b Dual gated ITO layer for enhanced phase shift up to 303^° at 1550 nm [52]. Reproduced with permission from ©2018, American Chemical Society. c Ionic-conduction-induced visible tunable meta-atom [40]. Reproduced with permission from ©2017, Wiley–VCH. d Oxide heterostructure for Berreman dispersion mode [53]. Reproduced with permission from ©2018, American Chemical Society