Negative refraction provides a route to steer and focus wave energy flow, but it remains difficult to realize for coherent terahertz phonons. The difficulty stems from conventional dispersion-based mechanisms, which require strongly anisotropic or negative-curvature dispersions, while the long-wavelength acoustic phonons most favorable for coherent transport are nearly isotropic. Here, we overcome this limitation by introducing a momentum compensation mechanism mediated by discrete translational symmetry. Discrete translational symmetry parallel to the interface supplies a compensating tangential momentum, reopening transmitted channels beyond the conventional critical condition and enabling negative refraction when this compensation reverses the tangential component. Mode-resolved calculations for hBN/graphene heterostructures establish this mechanism in laterally stitched in-plane interfaces and show how twisted van der Waals moiré superlattices shift the negative-refraction window to lower frequencies. These results identify periodic crystalline interfaces as symmetry-engineered elements for terahertz phonon momentum conversion and wavefront control.

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• Negative refraction
• Phononics
• Phonons
• Thermal boundary conductance
• Thermal transport
• Moire materials
• Solid-solid interfaces
• Twisted heterostructures
• First-principles calculations
• Machine learning
• Nonequilibrium Green's function
• S-matrix method in transport