Lattice vibrational modes and phonon thermal conductivity of single-layer GaGeTe

Exploring the vibrational properties of experimental or theoretical finding of new phase two-dimensional (2D) materials is one key to expand their promising application. The GaGeTe monolayer with high carrier mobility, tunable band structure, and low cleavage energy attracts rapidly growing interests in electronics. However, their vibrational modes and phonon properties are not explored. Based on first-principles calculations within the framework of density functional perturbation theory, we systematically study the lattice vibrational modes as well as phonon thermal conductivity of single-layer GaGeTe, which could be exfoliated from the experimentally synthesized GaGeTe crystal. We find that the frequencies and intensities of A1g and Eg Raman modes, contributing to the main peaks in Raman spectra of monolayer GaGeTe, show distinct responses to different external strains. The calculated lattice thermal conductivity of GaGeTe is about 58 Wm-1 K−1, which is comparable to that of MoS2 (around 52 Wm−1K−1) and two orders of magnitude lower than that of graphene (2000 Wm−1K−1) at room temperature. This is mainly due to the partial couple for acoustic branches and low frequency optic phonon branches, moderate group velocity, strong anharmonic ZA phonon branch. Moreover, atom substitution at tellurium could be as an effective strategy to further decrease lattice thermal conductivity. Our findings fill in the gap about the thermal transport properties of GaGeTe monolayer and trigger for further experimental verification of the predicted properties.