Charge Density Wave Transition in Monolayer CuTe driven by Coulomb Correlation

Dimensionality control provides a route to adjust physical properties in van der Waals layered materials. Bulk CuTe forming a layered structure exhibits a charge density wave (CDW) phase in Te chains with a periodicity of 5×1×2 at temperature below 335 K. The stability of the CDW state in a CuTe monolayer, however, has been investigated neither experimentally nor theoretically. Here, we report the theoretical prediction for the CDW phase in a CuTe monolayer using the first principles calculations. Similarly to its bulk structure, we find the phonon soft mode at q = (0.4, 0.0), indicating structural instability, which only appears with the correlation effect on Cu. The role of Coulomb correlations in driving the CDW transition suggests an electron-electron correlation and an electron-phonon interaction as the origin of the CDW instability. We expect the periodicity of the CDW phase in the CuTe monolayer to be 5×1. We show, by reducing the interlayer interactions, that tuning of the CDW modulation may be possible, as demonstrated by the modulation pattern in quasi-one-dimensional Te chains being different from that in the bulk counterpart.