Nanoscale Modulation of Flat Bands via Controllable Charge-Density-Waves Defects in 4Hb-TaS2

TL;DR

This study demonstrates how controllable charge-density-wave defects in 4Hb-TaS2 can modulate flat electronic bands, revealing new ways to manipulate electron correlations and quantum phases at the atomic scale.

Contribution

It introduces a method to create, erase, and control CDW defects in 4Hb-TaS2, elucidating their effects on flat bands through combined experimental and theoretical approaches.

Findings

Type 1 CDW defects suppress flat bands due to structural distortion.

Type 2 CDW defects increase flat band filling by reducing interlayer charge transfer.

STM manipulation enables atomic-scale control of CDW defects.

Abstract

Electron correlation is a main driver of exotic quantum phases and their interplay. The 4Hb-TaS2 system, possessing intrinsic heterostructure of 1T- and 1H-TaS2 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 (CDW) in the 1T layer of 4Hb-TaS2 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 lead 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.