  The incorporation of materials with controllable electromagnetic constitutive
parameters allows the conceptualization and realization of controllable
metasurfaces. With the aim of formulating and investigating a tricontrollable
metasurface for efficiently absorbing terahertz radiation, we adopted a
pixel-based approach in which the meta-atoms are biperiodic assemblies of
discrete pixels. We patched some pixels with indium antimonide (InSb) and some
with graphene, leaving the others unpatched. The bottom of each meta-atom was
taken to comprise a metal-backed substrate of silicon nitride. The InSb-patched
pixels facilitate the thermal and magnetic control modalities, whereas the
graphene-patched pixels facilitate the electrical control modality. With proper
configuration of patched and unpatched pixels and with proper selection of the
patching material for each patched pixel, the absorptance spectrums of the
pixelated metasurface were found to contain peak-shaped features with maximum
absorptance exceeding 0.95, full-width-at-half-maximum bandwidth of less than
0.7~THz, and the maximum-absorptance frequency lying between 2~THz and 4~THz.
The location of the maximum-absorptance frequency can be thermally,
magnetically, and electrically controllable. The lack of rotational invariance
of the optimal meta-atom adds mechanical rotation as the fourth control
modality.
