The Quantum Confinement Effect on the Spectrum of Near-Field Thermal Radiation by Quantum Dots

TL;DR

This paper investigates how quantum confinement in quantum dots influences the spectrum of near-field thermal radiation, demonstrating significant tunability of the LDOS peak wavenumber through size variation of the dots.

Contribution

It provides a detailed analysis of the size-dependent quantum confinement effects on near-field thermal radiation spectra of quantum dot arrays, including both periodic and random arrangements.

Findings

Peak wavenumber of LDOS can be modulated up to 4490 cm-1 by changing dot size.

LDOS peak is proportional to the imaginary part of QDs' polarizability, peaking at bandgap energy.

Quantum confinement significantly affects the peak wavenumber of radiative heat transfer.

Abstract

The quantum confinement effect on the spectrum of near-field thermal radiation by periodic and random arrays of quantum dots (QDs) is investigated. The local density of states (LDOS) thermally emitted by QD arrays made of three lead chalcogenides, namely, lead sulfide, lead selenide, and lead telluride, is computed at a near-field distance from the arrays. The dielectric function of the QDs is extracted from their absorption spectra by utilizing an optimization technique. The thermal discrete dipole approximation is used for computing the LDOS. It is shown that the peak wavenumber of near-field LDOS emitted by periodic arrays of lead chalcogenide QDs can be significantly modulated (up to 4490 cm-1) by varying the size of the dots. The LDOS is proportional to the imaginary part of the QDs' polarizability which peaks at the bandgap energy of the QDs. The bandgap energy of the QDs (and thus the LDOS peak) is significantly affected by the quantum confinement effect which is size-dependent. While the magnitude of thermal radiation by random arrays of QDs can be different from the periodic arrays with the same filling factor by up to 26%, the LDOS spectrum and peak location are the same for both periodic and random arrays. The peak wavenumber of near-field radiative heat transfer between the QD arrays is also strongly affected by quantum confinement in the QDs, and thus it can be tuned by changing the size of the QDs.