Tunable Interlayer Charge-transfer States in MoSe$_2$/WS$_2$ Moir\'e Superlattices

TL;DR

This study combines first-principles calculations and spectroscopy to explore tunable interlayer charge-transfer states and correlated phenomena in MoSe2/WS2 moiré superlattices, revealing controllable electron localization and charge orderings.

Contribution

It demonstrates the ability to control interlayer charge transfer and correlated states via electric fields in MoSe2/WS2 moiré superlattices, advancing understanding of their optical and electronic properties.

Findings

Observation of interlayer charge-transfer transitions from n/n0=1 to 4.

Electric field tuning switches band alignment from Type-I to Type-II.

Prediction of multiple correlated charge-ordered states at various fillings.

Abstract

Moir\'e superlattices formed by transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform for studying strongly correlated electronic, excitonic, and topological phenomena in solids. In particular, angle-aligned MoSe$_2$/WS$_2$ heterobilayers, which have a Type-I band alignment at zero vertical electric field, host rich correlated spin and charge physics. Here, combining large-scale first-principles calculations and optical reflection spectroscopy, we report a thorough study of the emergent moir\'e excitonic states and interlayer charge-transfer states in angle-aligned electron-doped MoSe$_2$/WS$_2$ moir\'e superlattices. The moir\'e excitonic states serve as sensitive optical probes to the localization profile of doped electrons. We observe a series of interlayer charge-transfer transitions from n/n$_0$ = 1 to 4 (where n$_0$ denotes the moir\'e density) when the vertical electric field switches the heterostructure band alignment from Type-I to Type-II. By tuning the vertical electric field, we can precisely control the interlayer electron localization, realizing a Fermi-Hubbard model with a tunable charge-transfer band on an effective honeycomb lattice. Furthermore, Monte Carlo simulation of the doping dependence of the electric-field susceptibility predicts that multiple correlated charge-ordered states appear at both integer and fractional fillings. Our results provide a holistic understanding of the emergent optical excitations and the correlated charge-transfer states in electron-doped MoSe$_2$/WS$_2$ moir\'e superlattices.