Work

Nanoscale modulation of flat bands via controllable charge density wave defects in 4 H b − Ta S 2

Year: 2025

Type: article

Abstract: Electron correlation is a main driver of exotic quantum phases and their interplay. The $4Hb\text{\ensuremath{-}}\text{Ta}{\mathrm{S}}_{2}$ system, possessing an intrinsic heterostructure of $1T$- and $1H\text{\ensuremath{-}}\text{Ta}{\mathrm{S}}_{2}$ monolayers, offers a unique opportunity to control electron correlation by distorting the atomic lattice or tuning interlayer coupling. Here, we investigated intrinsically deformed charge-density waves (CDWs) in the $1T$ layer of $4Hb\text{\ensuremath{-}}\text{Ta}{\mathrm{S}}_{2}$ to elucidate and control their effects on flat bands using scanning tunneling microscopy and spectroscopy (STM/S) combined with first-principles calculations. We identified two types of CDW defects: Type 1 has structural distortion and locally suppressed flat bands, while Type 2 features an increased flat band filling factor of intact CDW structure. Density functional theory calculations indicate that a sulfur vacancy in the $1T$ layer distorts the CDW structure and gives rise to a Type 1, whereas a sulfur vacancy in the $1H$ layer reduces the interlayer charge transfer and leads to a Type 2. Furthermore, we demonstrated creating and erasing individual CDW defects via STM manipulation. Our findings provide a pathway to not only tune flat bands but also selectively manipulate the interaction between CDW, the atomic lattice, and interlayer coupling in strongly correlated systems with atomic precision.

Source: Physical review. B./Physical review. B

DOI: 10.1103/lw6k-m6df