Atomistic Analysis of Room Temperature Quantum Coherence in Two-Dimensional CdSe Nanostructures

Area of Science:

• Materials Science
• Quantum Physics
• Nanotechnology

Background:

• Accurate measurement of quantum coherence in cadmium selenide (CdSe) nanoplatelets at room temperature is now possible due to precise synthesis techniques.
• Understanding the atomistic origins of coherence loss in these nanoscale materials is critical for their application in quantum technologies.

Purpose of the Study:

• To establish the atomistic origins of coherence loss between heavy and light hole excitations in 2D CdSe and CdSe/CdZnS core/shell nanoplatelets.
• To investigate the influence of defects, surfaces, and core/shell interfaces on quantum coherence.
• To provide insights into electron-phonon coupling in nanoscale materials.

Main Methods:

• Atomistic modeling using tight-binding density functional theory (DFT) and molecular dynamics (MD).
• Comparison of theoretical coherence times with experimentally measured values.
• Analysis of energy gap fluctuations and energy correlation decay between excited states.

Main Results:

• Coherence times calculated via MD simulations closely match experimental data.
• Long coherence times result from minimal energy gap fluctuations and slow energy correlation decay.
• Cationic defects significantly disrupt electronic structure and coherence, while anionic defects have minor effects.
• Heavy and light holes synchronize energy fluctuations by coupling to the same phonon modes, enabling long-lived coherence.
• Electronic excitations are localized near the surface, strongly coupling to surface acoustic phonons.

Conclusions:

• Quantum coherence in CdSe nanoplatelets is governed by specific defect types and electron-phonon coupling mechanisms.
• Understanding these factors is essential for designing and optimizing nanoscale quantum materials.
• The findings offer generalizable insights into quantum coherence in various nanoscale systems.