Extremely Large Response of Phonon Coherence in Twisted Penta-NiN₂ Bilayer

Twisting has recently been demonstrated as an effective strategy for tuning the interactions between particles or quasi-particles in layered materials. Motivated by the recent experimental synthesis of pentagonal NiN₂ sheet [ACS Nano 2021, 15, 13539], for the first time, the response of phonon coherence to twisting in bilayer penta-NiN₂ , going beyond the particle-like phonon transport is studied. By using the unified theory of phonon transport and high order lattice anharmonicity, together with the self-consistent phonon theory, it is found that the lattice thermal conductivity is reduced by 80.6% from 33.35 to 6.47 W m^-1 K^-1 at 300 K when the layers are twisted. In particular, the contribution of phonon coherence is increased sharply by an order of magnitude, from 0.21 to 2.40 W m^-1 K^-1 , due to the reduced differences between the phonon frequencies and enhanced anharmonicity after the introduction of twist. The work provides a fundamental understanding of the phonon interaction in twisted pentagonal sheets.