Continuous Mott transition in semiconductor moiré superlattices

Abstract

The interaction induced localization of electrons -the Mott transition -is expected to occur in the half-filled Hubbard model [1][2][3]24,25 . The ground state is a metal with a sharply defined electronic Fermi surface when the kinetic energy of the electrons -characterized by the bandwidth 𝑊far exceeds their interaction energy -characterized by the on-site Coulomb repulsion 𝑈 . Conversely, when 𝑈 ≫ 𝑊, the ground state is an electrical insulator with a charge-gap. The system undergoes a MIT when 𝑈 and 𝑊 become comparable. Although this picture is widely accepted from the seminal works of Mott and Hubbard, the nature of the transition remains poorly understood. In most materials, the transitions are driven first-order and often accompanied by simultaneous magnetic, structural or other forms of ordering 1,3 . Continuous MIT, which exhibits no symmetry

Multifaceted moiré superlattice physics in twisted WSe2 bilayers

“…The presence of a small misalignment angle θ or lattice mismatch δ between their constituent layers amplifies the atomic periodicity as a M = a/ √ θ 2 + δ 2 , with a the monolayer lattice constant. 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].…”

Dynamical mean field theory of moiré bilayer transition metal dichalcogenides: phase diagram, resistivity, and quantum criticality

“…Moiré bilayers have emerged as a fascinating system for exploration of correlated electron physics [1][2][3][4][5][6]. Moiré bilayers are formed when a monolayer of one material is placed on top of a monolayer of another material (heterobilayer) or when two layers of the same material (homobilayer) are stacked.…”

“…Bilayers are typically encapsulated with other materials for protection against degradation and to enable electrical contacts. In the heterobilayer case an in-plane moiré (very long period) superlattice may be generated when the two components have a lattice mismatch [5][6][7]. In the homobilayer case a moiré superlattice may be generated when the two layers are placed at a relative twist angle [3,4,8].…”

Simultaneous Control of Bandfilling and Bandwidth in Electric Double-Layer Transistor Based on Organic Mott Insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl

“…Moiré superlattices formed by atomic bilayers have recently emerged as a novel platform for correlated electron systems. Twisted bilayer graphene exhibits superconductivity and correlated insulating states [2], and transition metal dichalcogenide heterobilayers provide a correlation-tunable, Mott-insulating state on the triangular lattice [3]. These artificial systems are a powerful tool to understand the fundamental physics of quantum many-body systems.…”