First-principles Study on the Lattice Thermal Conductivity of Janus In2Ge2Te6 Bilayer

Janus In₂Ge₂Te₆ bilayer exhibit the potential for low thermal conductivity due to their complex geometry and large atomic mass contrast. The results demonstrate that the intersection of the low-frequency optical branch and the longitudinal acoustic phonon branch (LA) within the Janus In₂Ge₂Te₆ bilayer structure, combined with a larger average atomic mass, leads to a smaller phonon group velocity, a higher phonon scattering rate, a lower phonon relaxation time, and a stronger anharmonicity. These factors contribute to the lower thermal conductivity of the Janus In₂Ge₂Te₆ bilayer. The Janus In₂Ge₂Te₆ bilayer structure exhibits a maximum and minimum lattice thermal conductivity of about 0.35 and 0.1 W/(m K) at 300 and 1000 K, respectively.