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Title: Granular electronic systems.

Abstract

Granular metals are arrays of metallic particles of a size ranging usually from a few to hundreds of nanometers embedded into an insulating matrix. Metallic granules are often viewed as artificial atoms. Accordingly, granular arrays can be treated as artificial solids with programmable electronic properties. The ease of adjusting electronic properties of granular metals assures them an important role for nanotechnological applications and makes them most suitable for fundamental studies of disordered solids. This review discusses recent theoretical advances in the study of granular metals, emphasizing the interplay of disorder, quantum effects, fluctuations, and effects of confinement. These key elements are quantified by the tunneling conductance between granules g, the charging energy of a single granule E{sub c}, the mean level spacing within a granule {delta}, and the mean electronic lifetime within the granule {h_bar}/g{delta}. By tuning the coupling between granules the system can be made either a good metal for g>gc=(1/2pid)ln(Ec/{delta}) (d is the system dimensionality), or an insulator for g<gc. The metallic phase in its turn is governed by the characteristic energy Gamma=gdelta: at high temperatures T>Gamma the resistivity exhibits universal logarithmic temperature behavior specific to granular materials, while at T<Gamma the transport properties are those generic formore » all disordered metals. In the insulator phase the transport exhibits a variety of activation behaviors including the long-puzzling {sigma}{approx}exp[-(T0/T)1/2] hopping conductivity. Superconductivity adds to the richness of the observed phases via one more energy parameter {Delta}. Using a wide range of recently developed theoretical approaches, it is possible to obtain a detailed understanding of the electronic transport and thermodynamic properties of granular materials, as is required for their applications.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); DFG; DIP; Alexander von Humboldt Foundation
OSTI Identifier:
915028
Report Number(s):
ANL/MSD/JA-59748
Journal ID: ISSN 0034-6861; RMPHAT; TRN: US200817%%69
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Rev. Mod. Phys.; Journal Volume: 79; Journal Issue: 2 ; Apr. 2, 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; GRANULAR MATERIALS; METALS; ELECTRICAL PROPERTIES; NANOSTRUCTURES; LIFETIME; SUPERCONDUCTIVITY; THERMODYNAMIC PROPERTIES

Citation Formats

Beloborodov, I. S., Lopatin, A. V., Vinokur, V. M., Efetov, K. B., Materials Science Division, Ruhr-Univ. Bochum, and Landau Inst. Theor. Phys. Granular electronic systems.. United States: N. p., 2007. Web. doi:10.1103/RevModPhys.79.469.
Beloborodov, I. S., Lopatin, A. V., Vinokur, V. M., Efetov, K. B., Materials Science Division, Ruhr-Univ. Bochum, & Landau Inst. Theor. Phys. Granular electronic systems.. United States. doi:10.1103/RevModPhys.79.469.
Beloborodov, I. S., Lopatin, A. V., Vinokur, V. M., Efetov, K. B., Materials Science Division, Ruhr-Univ. Bochum, and Landau Inst. Theor. Phys. Mon . "Granular electronic systems.". United States. doi:10.1103/RevModPhys.79.469.
@article{osti_915028,
title = {Granular electronic systems.},
author = {Beloborodov, I. S. and Lopatin, A. V. and Vinokur, V. M. and Efetov, K. B. and Materials Science Division and Ruhr-Univ. Bochum and Landau Inst. Theor. Phys.},
abstractNote = {Granular metals are arrays of metallic particles of a size ranging usually from a few to hundreds of nanometers embedded into an insulating matrix. Metallic granules are often viewed as artificial atoms. Accordingly, granular arrays can be treated as artificial solids with programmable electronic properties. The ease of adjusting electronic properties of granular metals assures them an important role for nanotechnological applications and makes them most suitable for fundamental studies of disordered solids. This review discusses recent theoretical advances in the study of granular metals, emphasizing the interplay of disorder, quantum effects, fluctuations, and effects of confinement. These key elements are quantified by the tunneling conductance between granules g, the charging energy of a single granule E{sub c}, the mean level spacing within a granule {delta}, and the mean electronic lifetime within the granule {h_bar}/g{delta}. By tuning the coupling between granules the system can be made either a good metal for g>gc=(1/2pid)ln(Ec/{delta}) (d is the system dimensionality), or an insulator for g<gc. The metallic phase in its turn is governed by the characteristic energy Gamma=gdelta: at high temperatures T>Gamma the resistivity exhibits universal logarithmic temperature behavior specific to granular materials, while at T<Gamma the transport properties are those generic for all disordered metals. In the insulator phase the transport exhibits a variety of activation behaviors including the long-puzzling {sigma}{approx}exp[-(T0/T)1/2] hopping conductivity. Superconductivity adds to the richness of the observed phases via one more energy parameter {Delta}. Using a wide range of recently developed theoretical approaches, it is possible to obtain a detailed understanding of the electronic transport and thermodynamic properties of granular materials, as is required for their applications.},
doi = {10.1103/RevModPhys.79.469},
journal = {Rev. Mod. Phys.},
number = 2 ; Apr. 2, 2007,
volume = 79,
place = {United States},
year = {Mon Apr 02 00:00:00 EDT 2007},
month = {Mon Apr 02 00:00:00 EDT 2007}
}
  • The electrical properties of Fe-SiO{sub 2} have been studied in the low-field regime (eΔV ≪ k{sub B}T), varying the injected current and the bias potential. Superparamagnetism and a resistance drop of 4400 Ω (for a voltage variation of 15 V) were observed at room temperature. This resistance drop increased at lower temperatures. The electrical properties were described with the “Mott variable range hopping” model explaining the behavior of the electrical resistance and the electronic localization length as due to the activation of new electronic paths between more distant grains. This non-ohmic resistance at room temperature can be important for properties dependent ofmore » electrical current (magnetoresistance, Hall effect, and magnetoimpedance).« less
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  • A one-dimensional chain of superconducting granules with Josephson coupling between them is considered. The absence of long-range order in the phase below T/sub c/ for such a system leads to the existence of a unique ''paraconductivity'' due to the superconducting state of the granules, which is calculated exactly for the given model. (AIP)
  • The short-term memory effects recently observed in vibration-induced compaction of granular materials are studied. It is shown that they can be explained by means of quite plausible hypothesis about the mesoscopic description of the evolution of the system. The existence of a critical time separating regimes of {open_quotes}anomalous{close_quotes} and {open_quotes}normal{close_quotes} responses is predicted. A simple model fitting into the general framework is analyzed in the detail. The relationship between this paper and previous studies is discussed.