Valley Polarization in Size-Tunable Monolayer Semiconductor Quantum Dots

TL;DR

This paper demonstrates that monolayer MoS₂ quantum dots, created via top-down nanofabrication, retain valley polarization and exhibit size-dependent excitonic energies, enabling their use in quantum information and spintronics.

Contribution

It introduces a new method to create monolayer MoS₂ quantum dots that preserve valley polarization, integrating 2D materials into complex quantum devices.

Findings

Monolayer MoS₂ QDs exhibit valley polarization similar to continuous monolayers.

Quantum dots show size-dependent excitonic energies.

Fabrication process is compatible with semiconductor technology.

Abstract

Three-dimensional confinement allows semiconductor quantum dots (QDs) to exhibit size-tunable electronic and optical properties that enable a wide range of opto-electronic applications from displays, solar cells and bio-medical imaging to single-electron devices. Additional modalities such as spin and valley properties can provide further degrees of freedom requisite for quantum information and spintronics. When seeking to combine these material features into QD structures, however, confinement can cause hybridization that inhibits the robustness of these emergent properties for insertion into quantum devices. Here, we show that a new class of laterally-confined materials, monolayer MoS$_2$ QDs, can be created through top-down nanopatterning of an atomically-thin two-dimensional semiconductor so that they exhibit the same valley polarization as in a continuous monolayer sheet. Semiconductor-compatible nanofabrication process allows for these low-dimensional materials to be integrated into complex systems, an important feature for advancing quantum information applications. The inherited bulk spin and valley properties, the size dependence of excitonic energies, and the ability to fabricate MoS$_2$ QDs using semiconductor-compatible processing suggest that monolayer semiconductor QDs have the potential to be multimodal building blocks of integrated quantum information and spintronics systems.