Terahertz conductivity of the metal-insulator transition in a nanogranular VO2 film

Cocker, Tyler L.; Titova, Lyubov V.; Fourmaux, S.; Bandulet, H.; Brassard, D.; Kieffer, Jean‐Claude; Khakani, My Alì El; Hegmann, Frank A.

doi:10.1063/1.3518482

Cited by 95 publications

(100 citation statements)

References 25 publications

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“…Such a system will exhibit persistent carrier confinement, resulting in a suppression of the DC conductivity, 18,26 whereas Bruggeman EMT would predict a Drude-like effective conductivity if the microscopic metallic conductivity were assumed to be Drude.…”

Section: −48mentioning

confidence: 99%

“…(Previously, a scaling factor of this type was associated with the metallic filling fraction. 26 ) Nevertheless, depolarization fields do play an important role in determining the macroscopic THz conductivities of some non-percolated systems. [64][65][66][67][70][71][72][73][74] In these cases, the strong dependence of depolarization-based conductivity suppression on car-rier density can be used to distinguish it from weak carrier confinement, though it remains unclear how best to combine the two effects.…”

Section: −48mentioning

confidence: 99%

“…23,29,[34][35][36]39,71,73,76 Alternatively, the Drude-Smith model has also been used as an EMT in its own right and fit directly to the measured THz conductivity. [9][10][11][12][13][14][15][16][17][18][19]21,22,[25][26][27]30,31,33,38,[41][42][43][44][45]48 Each approach begins with a different physical process and leads to its own difficulties when one interprets the subsequent fits to the data. In the former case, depolarization fields are included explicitly and treated as independent from weak confinement.…”

Section: −48mentioning

confidence: 99%

“…76,77 Fitting these simulations enabled Nemȇc et al to provide approximate mathematical expressions for the Drude-Smith fit parameters 76 that have since been applied to experimental data to extract meaningful physical information. 15,26,27,33,38 Complementary experimental techniques are often also used to examine the structure 11,12,15,[17][18][19][20]22,23,25,26,29,31,[33][34][35][36][37][38][39][41][42][43][44]46,47,50 and carrier transport characteristics 11,12,19,23,26,43,57 in a sample to test the fidelity of the Drude-Smith fits. Nevertheless, in the absence of a tractable derivation that shows how weak carrier confinement yields the DrudeSmith formula with well-understood fit parameters, it is difficult for the Drude-Smith model to be more than a convenient expression for linking the conductivities of similar nanosystems to one another, and to Monte Carlo simulations.…”

Section: −48mentioning

confidence: 99%

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Microscopic origin of the Drude-Smith model

et al. 2017

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The Drude-Smith model has been used extensively in fitting the THz conductivities of nanomaterials with carrier confinement on the mesoscopic scale. Here, we show that the conventional 'backscattering' explanation for the suppression of low-frequency conductivities in the Drude-Smith model is not consistent with a confined Drude gas of classical non-interacting electrons and we derive a modified Drude-Smith conductivity formula based on a diffusive restoring current. We perform Monte Carlo simulations of a model system and show that the modified Drude-Smith model reproduces the extracted conductivities without free parameters. This alternate route to the DrudeSmith model provides the popular formula with a more solid physical foundation and well-defined fit parameters.

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Section: −48mentioning

confidence: 99%

Section: −48mentioning

confidence: 99%

Section: −48mentioning

confidence: 99%

Section: −48mentioning

confidence: 99%

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Microscopic origin of the Drude-Smith model

et al. 2017

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“…It is of interest to know what happen in inhomogeneous media. It is known that a deviation from Drude behavior is observed in most electronically conductive nanostructured materials, such as metals [4][5][6], semiconductors [7][8][9][10][11][12][13][14][15][16], and oxides [17][18][19]. The non-Drude behavior in nanomaterials is a kind of Lorentz resonance.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Carrier Transport in Nanoscale Materials: Origin of Non-Drude Behavior in the Terahertz Frequency Range

Shimakawa

Kasap

2016

Applied Sciences

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Abstract:It is known that deviation from the Drude law for free carriers is dramatic in most electronically conductive nanomaterials. We review recent studies of the conductivity of nanoscale materials at terahertz (THz) frequencies. We suggest that among a variety of theoretical formalisms, a model of series sequence of transport involving grains and grain boundaries provides a reasonable explanation of Lorentz-type resonance (non-Drude behavior) in nanomaterials. Of particular interest is why do free carriers exhibit a Lorentz-type resonance.

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Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

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Transport of charges is a fundamental process in many high-tech applications including photovoltaic or optoelectronic devices, but also in more ordinary components such as unsophisticated wires and other circuitry. The development of nanotechnologies resulted in the fabrication of highly complex materials consisting of a large variety of nanosized elements, which inevitably involve a multitude of charge transport processes occurring on various time-and length-scales. Figure 1 summarizes the most common nanoelements with high application potential.For example, the electrodes employed in Grätzel solar cells [1] are composed of percolated networks of a huge number of metal oxide nanoparticles (top-left panel in Figure 1). Colloidal nanocrystals form the basis for thin film electronics and flexible electronic devices. [2] The synthetic approaches control their composition, size and electronic structure (energy levels, density of states within the bands and in the bandgap) and the charge-carrier transport. [2,3] Nanowires and nanotubes made of conventional semiconductors are quasi 1D systems combining Terahertz spectroscopy has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes or 2D crystals. Its great importance stems from the fact that it is a noncontact method and, owing to its high frequency and broadband character, it is capable of characterizing charge transport properties within individual nano-objects but also among them. In addition, probing of photoinitiated ultrafast charge dynamics is possible thanks to the sub-picosecond time resolution. Despite this unprecedented potential, the interpretation of the measured terahertz conductivity spectra in many materials is still intensively debated. Herein is presented a review of the experiments performed on nanostructures of conventional semiconductors and on carbon nanomaterials (graphene and carbon nanotubes) during the past decade. The state of the art of the theoretical formalism is provided and discussed, including the intrinsic response, as well as the role of inherent heterogeneity and of the experimental conditions.

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Terahertz conductivity of the metal-insulator transition in a nanogranular VO2 film

Cited by 95 publications

References 25 publications

Microscopic origin of the Drude-Smith model

Microscopic origin of the Drude-Smith model

Dynamics of Carrier Transport in Nanoscale Materials: Origin of Non-Drude Behavior in the Terahertz Frequency Range

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

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