Correlated Quantum Phenomena in Confined Two-Dimensional Hexagonal Crystals

TL;DR

This review discusses how quantum confinement in two-dimensional hexagonal materials like graphene and TMDs enhances Coulomb interactions, leading to novel correlated quantum phenomena with potential applications.

Contribution

It provides a comprehensive overview of recent experimental and theoretical advances on confinement-induced correlated states in 2D hexagonal materials.

Findings

Confinement in quantum dots leads to discrete spectra with amplified interactions.

Moiré superlattices induce nontrivial band topology and emergent phenomena.

Reduced dimensionality promotes diverse correlated quantum states.

Abstract

Low-energy fermionic excitations in two-dimensional materials deviate from the conventional Schr\"odinger description and are instead governed by Dirac equations. Such Dirac fermions give rise to a variety of unconventional quantum phenomena that have no direct analogues in traditional condensed matter systems. Among these materials, graphene and transition metal dichalcogenides (TMDs) represent two prototypical platforms, hosting massless and massive Dirac particles, respectively, and exhibiting rich electronic, optical, and valley dependent properties. Here we review the effect of the quantum confinement in these two-dimensional hexagonal materials that provides a powerful route to enhance Coulomb interactions and stabilizing correlated quantum states. In graphene- and TMD-based quantum dots, externally imposed confinement leads to discrete electronic and excitonic spectra, where interaction effects are strongly amplified. In twisted van der Waals heterostructures, the moir\'e superlattices generate emergent confinement and induce nontrivial band topology, giving rise to a wealth of novel phenomena. More generally, reduced dimensionality and spatial localization in two-dimensional materials promote a diverse range of correlated states. Recent experimental and theoretical advances highlight the central role of confinement in shaping quantum behavior and reveal new opportunities for applications based on these states. In this review, we provide an overview of recent progress in confinement-induced correlated phenomena in two-dimensional materials from both theoretical and experimental perspectives.