  Two-dimensional (2D) materials are able to strongly confine light hybridized
with collective excitations of atoms, enabling electric-field enhancements and
novel spectroscopic applications. Recently, freestanding monolayers of oxide
perovskites have been synthesized, which possess highly infrared-active phonon
modes and a complex interplay of competing interactions. In this study, we
evaluate central figures of merit for phonon polaritons in the tetragonal
phases of the 2D perovskites SrTiO$_3$, KTaO$_3$, and LiNbO$_3$, using density
functional theory calculations. Specifically, we compute the 2D
phonon-polariton dispersions, the propagation-quality, confinement, and
deceleration factors, and we show that they are comparable to those found in
the prototypical 2D dielectric hexagonal boron nitride. Our results suggest
that monolayers of oxide perovskites are promising candidates for polaritonic
platforms in the terahertz spectral range that enable possibilites to control
complex phases of matter through strongly enhanced electromagnetic fields.
