Anharmonicity Reveals the Tunability of the Charge Density Wave Orders in Monolayer VSe2

VSe2 is a layered compound that has attracted great attention due to its proximity to a ferromagnetic state that is quenched by its charge density wave (CDW) phase. In the monolayer limit, unrelated experiments have reported different CDW orders with different transition temperatures, making this monolayer very controversial. Here we perform first-principles nonperturbative anharmonic phonon calculations in monolayer VSe2 in order to estimate the CDW order and the corresponding transition temperature. They reveal that monolayer VSe2 develops two independent charge density wave orders that compete as a function of strain. Variations of only 1.5% in the lattice parameter are enough to stabilize one order or the other. Moreover, we analyze the impact of external Lennard-Jones interactions, showing that these can act together with anharmonicity to suppress the CDW orders. Our results solve previous experimental contradictions, highlighting the high tunability and substrate dependency of the CDW orders of monolayer VSe2.

Automated summary

In this study, nonperturbative anharmonic phonon calculations were performed to investigate monolayer VSe2. It was found that monolayer VSe2 exhibits two independent charge density wave (CDW) orders that compete with each other under strain. Even slight variations in the lattice parameter are sufficient to stabilize one of the CDW orders. Additionally, the impact of external Lennard-Jones interactions was analyzed, revealing their ability to suppress the CDW orders in conjunction with anharmonicity. These findings resolve previous experimental contradictions and highlight the high tunability and substrate dependency of the CDW orders in monolayer VSe2.