Interferences of electrostatic moiré potentials and bichromatic superlattices of electrons and excitons in transition metal dichalcogenides

Abstract

Recent experimental progresses have demonstrated the great potential of electronic and excitonic moiré superlattices in transition metal dichalcogenides (TMDs) for quantum many-body simulations and quantum optics applications. Here we reveal that the moiré potential landscapes in the TMDs heterostructures have an electrostatic origin from the spontaneous charge transfer across the heterointerfaces dependent on the atomic registry. This allows engineering tunable multi-chromatic superlattices through the interference of moiré potentials from independently configurable heterointerfaces in multilayers. We show examples of bichromatic moiré potentials for valley electrons, holes, and interlayer trions in MX2/M’X’2/MX2 trilayers, which can be strain switched from multi-orbital periodic superlattices to quasi-periodic disordered landscape. The trilayer moiré also hosts two independently configurable triangular superlattices of neutral excitons with opposite electric dipoles. These findings greatly enrich the versatility and controllability of TMDs moiré as a quantum simulation platform.

Weak ferroelectric charge transfer in layer-asymmetric bilayers of 2D semiconductors

“…This is usually achieved by the construction of a supercell in which images of the two-dimensional (2D) layers are repeated periodically along the third dimension, with a large vacuum between them to ensure the layers are isolated from each other. Here, we compare results for polar bilayers using three commonly-used methods of addressing the requirement for periodicity in first-principles calculations of 2D materials: (1) a supercell with a single bilayer 7 , (2) a single bilayer supercell, but with a dipole correction applied 11 , and (3) a supercell with two mirror-reflected images of the bilayer 3 .…”

Multifaceted moiré superlattice physics in twisted WSe2 bilayers

“…Moiré superlattices induce a plethora of physical effects, such as long-range interlayer hybridization, leading to flat minibands with strongly correlated electronic states [2][3][4][5][6][7][8][9][10] and minibands for excitons in transition metal dichalcogenide (TMD) bilayers [11,12] at twist angles θ 10 • , for which the moiré periodicity exceeds the exciton Bohr radius, thus affecting the system's optoelectronic properties [13][14][15][16][17]. Moreover, piezoelectric effects caused by lattice reconstruction in TMD bilayers [1,18,19] create periodic traps for charge carriers [20,21] and excitons [22], whereas interlayer charge transfer [23,24] induces ferroelectric polarization in these structures [25][26][27].…”

“…In-plane lattice reconstruction is accompanied by interlayer distance modulation across the supercell, which is of especial importance for the hybridization of the top valence band states at the valley, formed by d z 2 and p z orbitals of metals and chalcogens, respectively. A theoretical analysis of the electron properties in twisted TMD homobilayers must take into account the competition between various comparable factors, such as the piezoelectric potential, variation of the local band structure throughout the moiré superlattice with local stacking and interlayer distance, and interlayer (ferroelectric) charge transfer, relevant for P bilayers [23,24].…”

Local Sensing of Correlated Electrons in Dual-moiré Heterostructures using Dipolar Excitons

“…Taking a first step towards this approach, we study a dual-moiré WSe 2 /MoSe 2 /WSe 2 heterotrilayer which features different moiré superlattices for electrons and dipolar interlayer excitons, owing to different twist angles of the top and bottom heterobilayers [19]. Moiré-trapped interlayer excitons (IX) with stable and spectrally narrow emission, together with an out-ofplane, non-oscillating dipole, respond sensitively to electric fields by changing their emission energy, thus becoming local sensors of charge distribution around them.…”

“…1C, which plots the calculated moiré potentials for an IX in the bottom heterobilayer and an electron in the MoSe 2 layer for twist angles of 1 • /4 • , representative of our sample. While an IX experiences only the bottom moiré potential, an electron sees the interference of the top and bottom moiré potentials resulting in a multi-orbital (multi-minima) electron moiré potential [19].…”