Embedded Eigenstate Enables Perfect Absorption Tunable with Twist

Here, we investigate a heterostructure supporting embedded eigenstates (EEs) governed by phonon-polariton resonances in anisotropic quasi-2D MoO
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layers in the IR spectral range tuned with a relative rotation of the layers. We demonstrate that the structure can be tuned from an almost perfect reflector to an almost perfect absorber and back near the EE state. The approach paves the way to reconfigurable absorbers, quasi-coherent thermal emitters and other active photonic elements.