Charge Density Wave Activated Excitons in TiSe${}_2$-MoSe${}_2$ Heterostructures

Abstract

Layered materials enable the assembly of a new class of heterostructures where lattice-matching is no longer a requirement. Interfaces in these heterostructures therefore become a fertile ground for unexplored physics as dissimilar phenomena can be coupled via proximity effects. In this article we identify an unexpected photoluminescence (PL) peak when MoSe${}_2$ interacts with TiSe${}_2$. A series of temperature-dependent and spatially-resolved PL measurements reveal this peak is unique to the TiSe${}_2$-MoSe${}_2$ interface, higher in energy compared to the neutral exciton, and exhibits exciton-like characteristics. The feature disappears at the TiSe${}_2$ charge density wave transition, suggesting that the density wave plays an important role in the formation of this new exciton. We present several plausible scenarios regarding the origin of this peak that individually capture some aspects of our observations, but cannot fully explain this feature. These results therefore represent a fresh challenge for the theoretical community and provide a fascinating way to engineer excitons through interactions with charge density waves.

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Cited by in corpus (3)

• Leaky exciton condensates in transition metal dichalcogenide moiré bilayers
• Emergent bright excitons with Rashba spin-orbit coupling in atomic monolayers
• Tunable resonant s-p mixing of excitons in van der Waals heterostructures