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Title: Metal-Insulator Transition in Nanoparticle Solids: Insights from Kinetic Monte Carlo Simulations

Progress has been rapid in increasing the efficiency of energy conversion in nanoparticles. However, extraction of the photo-generated charge carriers remains challenging. Encouragingly, the charge mobility has been improved recently by driving nanoparticle (NP) films across the metal-insulator transition (MIT). To simulate MIT in NP films, we developed a hierarchical Kinetic Monte Carlo transport model. Electrons transfer between neighboring NPs via activated hopping when the NP energies differ by more than an overlap energy, but transfer by a non-activated quantum delocalization, if the NP energies are closer than the overlap energy. As the overlap energy increases, emerging percolating clusters support a metallic transport across the entire film. We simulated the evolution of the temperature-dependent electron mobility. We analyzed our data in terms of two candidate models of the MIT: (a) as a Quantum Critical Transition, signaled by an effective gap going to zero; and (b) as a Quantum Percolation Transition, where a sample-spanning metallic percolation path is formed as the fraction of the hopping bonds in the transport paths is going to zero. We found that the Quantum Percolation Transition theory provides a better description of the MIT. We also observed an anomalously low gap region next to the MIT.more » We discuss the relevance of our results in the light of recent experimental measurements.« less
Authors:
 [1] ; ORCiD logo [2] ;  [1]
  1. Univ. of California, Davis, CA (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
National Science Foundation (NSF); USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
OSTI Identifier:
1392500

Qu, Luman, Vörös, Márton, and Zimanyi, Gergely T. Metal-Insulator Transition in Nanoparticle Solids: Insights from Kinetic Monte Carlo Simulations. United States: N. p., Web. doi:10.1038/s41598-017-06497-1.
Qu, Luman, Vörös, Márton, & Zimanyi, Gergely T. Metal-Insulator Transition in Nanoparticle Solids: Insights from Kinetic Monte Carlo Simulations. United States. doi:10.1038/s41598-017-06497-1.
Qu, Luman, Vörös, Márton, and Zimanyi, Gergely T. 2017. "Metal-Insulator Transition in Nanoparticle Solids: Insights from Kinetic Monte Carlo Simulations". United States. doi:10.1038/s41598-017-06497-1. https://www.osti.gov/servlets/purl/1392500.
@article{osti_1392500,
title = {Metal-Insulator Transition in Nanoparticle Solids: Insights from Kinetic Monte Carlo Simulations},
author = {Qu, Luman and Vörös, Márton and Zimanyi, Gergely T.},
abstractNote = {Progress has been rapid in increasing the efficiency of energy conversion in nanoparticles. However, extraction of the photo-generated charge carriers remains challenging. Encouragingly, the charge mobility has been improved recently by driving nanoparticle (NP) films across the metal-insulator transition (MIT). To simulate MIT in NP films, we developed a hierarchical Kinetic Monte Carlo transport model. Electrons transfer between neighboring NPs via activated hopping when the NP energies differ by more than an overlap energy, but transfer by a non-activated quantum delocalization, if the NP energies are closer than the overlap energy. As the overlap energy increases, emerging percolating clusters support a metallic transport across the entire film. We simulated the evolution of the temperature-dependent electron mobility. We analyzed our data in terms of two candidate models of the MIT: (a) as a Quantum Critical Transition, signaled by an effective gap going to zero; and (b) as a Quantum Percolation Transition, where a sample-spanning metallic percolation path is formed as the fraction of the hopping bonds in the transport paths is going to zero. We found that the Quantum Percolation Transition theory provides a better description of the MIT. We also observed an anomalously low gap region next to the MIT. We discuss the relevance of our results in the light of recent experimental measurements.},
doi = {10.1038/s41598-017-06497-1},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {2017},
month = {8}
}

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