Correlated electrons of the flat band in charge density wave state of 4Hb-TaSexS2-x

Many intriguing quantum states of matter, such as unconventional superconductivity, magnetic phases and fractional quantum Hall physics, emergent from the spatially-correlated localized electrons in the flat band of solid materials. By using scanning tunneling microscopy and spectroscopy (STM/STS), we report the real-space investigation of correlated electrons in the flat band of superlattice 4Hb-TaSexS2-x. In contrast with the pristine 4Hb-TaS2, the selenium (Se) substitutions significantly affect the interfacial transfer of correlated electrons between the CDW states of 1T- and 1H-TaS2 layers, and contribute a real-space fractional electron-filling configurations with the distributed electron-filled and -void SoD clusters of 1T-layer. The site-specific STS spectra directly reveal their respective prominent spectra weight above EF and symmetric Mott-like spectra. In addition, the spatial distributions of these electron-filled SoDs in the 1T-layer of 4Hb-TaSe0.7S1.3 demonstrate different local short-range patterning, clearly indicating the complex neighboring interactions among the localized electrons in the flat band of 1T-layer. Our results not only provide an in-depth insight of correlated electrons in the flat CDW band, and provide a simple platform to manipulate the electron-correlation-related quantum states.