Phonon-enhanced strain sensitivity of quantum dots in two-dimensional semiconductors

TL;DR

This study demonstrates that quantum dots in two-dimensional semiconductors exhibit significantly enhanced strain sensitivity due to phonon interactions, offering a new approach for spectral tuning in quantum photonic applications.

Contribution

It reveals the phonon-mediated enhancement of strain sensitivity in quantum dots within 2D semiconductors, advancing strain engineering for quantum photonics.

Findings

Quantum dots show fourfold increased strain sensitivity in WS₂.

Quantum dots show twofold increased strain sensitivity in WSe₂.

Enhanced strain sensitivity is linked to phonon interactions and quantum confinement.

Abstract

Two-dimensional semiconductors have attracted considerable interest for integration into emerging quantum photonic networks. Strain engineering of monolayer transition-metal dichalcogenides (ML-TMDs) enables the tuning of light-matter interactions and associated optoelectronic properties, and generates new functionalities, including the formation of quantum dots (QDs). Here, we combine spatially resolved micro-photoluminescence ($\mu$-PL) spectroscopy from cryogenic (4$\text{-}$94 K) to room temperature with micro-Raman spectroscopy at room temperature to investigate the strain-dependent emission energies of thousands of individual QDs in ML-WS$_2$ and ML-WSe$_2$, integrated across multiple heterostructures and a piezoelectric device. Compared with delocalized excitons, QDs in both materials exhibit enhanced strain sensitivities of their emission energies $-$ approximately fourfold in WS$_2$ and twofold in WSe$_2$ $-$ leading to pronounced broadening of the ensemble emission linewidth. Temperature-dependent $\mu$-PL spectroscopy combined with dynamic strain tuning experiments further reveal that the enhanced strain sensitivity of individual QDs originates from strengthened interactions with low-energy phonons induced by quantum confinement. Our results demonstrate a versatile strain-engineering approach with potential for spectral matching across solid-state, atomic, and hybrid quantum photonic networks, and provide new insights into phonon-QD interactions in two-dimensional semiconductors.