Nonlinear dc conductivity in disordered metals near the metal-insulator transition

Osofsky, M. S.; LaMadrid, Marissa; Jb, Bieri; Contrata, W.; Gavilano, J. L.; Jm, Mochel

doi:10.1103/physrevb.38.8486

Cited by 10 publications

(4 citation statements)

References 15 publications

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“…This behavior can be observed in a dielectric illuminated by a Laser [2] when the multiphoton processes dominates and the usual linear approximation completely breaks down. Certain cermets resistors, ZnO based varistors [14,15] or disordered alloys [16] can also display this behavior (1). In a disordered medium, the nonlinear susceptibilities χ can fluctuate from point to point and one is interested in the macroscopic effective behavior of such a medium.…”

mentioning

confidence: 99%

Path-integral approach to strongly nonlinear composites

Barthélemy

2000

Phys. Rev. B

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We study strongly nonlinear disordered media using a functional method. We solve exactly the problem of a nonlinear impurity in a linear host and we obtain a Bruggeman-like formula for the effective nonlinear susceptibility. This formula reduces to the usual Bruggeman effective medium approximation in the linear case and has the following features: (i) It reproduces the weak contrast expansion to the second order and (ii) the effective medium exponent near the percolation threshold are s = 1, t = 1 + κ, where κ is the nonlinearity exponent. Finally, we give analytical expressions for previously numerically calculated quantities.

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mentioning

confidence: 99%

Path-integral approach to strongly nonlinear composites

Barthélemy

2000

Phys. Rev. B

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“…21−24 In metallic systems near MIT, σ ∝ E 1/3 has been reported. 25 The field-dependent transport in this work is observed not to follow these conventional models, as the field effects on nanoscale networks of localized-delocalized states in conducting polymer chains are quite different. Also, the thermal and field effects compete, and the field dependence of conductivity weakens at T > 100 K. Since the delocalization and conductivity in PEDOT:PSS can be easily tuned, the scaling behavior of the field and temperature-dependent conductivity of samples near MIT is yet to be investigated.…”

Section: Introductionmentioning

confidence: 62%

“…In the case of insulators with hopping transport, the energy gained from the electric field usually increases the hopping length and conductivity, though its functional form depends on disorder and carrier density. At moderate electric fields, conductivity follows lnσ ∝ E 2 and lnσ ∝ E , and at higher electric fields, the exponent can vary [lnσ ∝ E n , where n = 1/2 or 1/4]. − In metallic systems near MIT, σ ∝ E 1 / 3 has been reported . The field-dependent transport in this work is observed not to follow these conventional models, as the field effects on nanoscale networks of localized-delocalized states in conducting polymer chains are quite different.…”

Section: Introductionmentioning

confidence: 65%

Tuning the Conductivity by Disorder and Electric Field Near the Metal–Insulator Transition

Mohan,

Menon

2024

J. Phys. Chem. C

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The electric field-dependent conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) [PEDOT:PSS], from metallic to insulator, is investigated in a temperature range of 4.2–200 K. The conductivity of PEDOT:PSS is systematically varied from 36 to 1070 S/cm, with the addition of dimethyl sulfoxide (DMSO) and ethylene glycol (EG). As the delocalization increases, the onset of increase in conductivity occurs at lower fields. The field-dependent conductivity fits to a power law, and the values of the field-induced delocalization length (L E ) are estimated. L E increases at low temperatures for metallic samples and decreases for insulators. The data for all samples collapse onto the scaling function fit at all temperatures. This scaling fit shows that the field enhances the correlated transport among delocalized states and increases the conductivity. The J/T 1+α vs eV/k B T analysis for metallic and critical samples collapses onto a straight line fit, and it deviates for the insulating sample.

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“…The fitted line when extrapolated yields x min T ∼ 7. Also shown in the figure are the data (closed circles) from two thick films (thickness 140-150 nm) of Ge 0.79 Au 0.21 and C x Cu 1−x measured by Osofsky et al 30 . Authors considered the films to be three dimensional and on the metallic side of the MIT, and analyzed the data using McMillan's scaling theory 31 .…”

Section: Scaling In Two Dimension (2d)mentioning

confidence: 99%

Universal scaling in disordered systems and nonuniversal exponents

Bardhan

Talukdar

Nandi³

et al. 2014

Phys. Rev. B

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The effect of an electric field on conduction in a disordered system is an old but largely unsolved problem. Experiments cover an wide variety of systems -amorphous/doped semiconductors, conducting polymers, organic crystals, manganites, composites, metallic alloys, double perovskitesranging from strongly localized systems to weakly localized ones, from strongly correlated ones to weakly correlated ones. Theories have singularly failed to predict any universal trend resulting in separate theories for separate systems. Here we discuss an one-parameter scaling that has recently been found to give a systematic account of the field-dependent conductance in two diverse, strongly localized systems of conducting polymers and manganites. The nonlinearity exponent, x associated with the scaling was found to be nonuniversal and exhibits structure. For two-dimensional (2D) weakly localized systems, the nonlinearity exponent x is 7 and is roughly inversely proportional to the sheet resistance. Existing theories of weak localization prove to be adequate and a complete scaling function is derived. In a 2D strongly localized system a temperature-induced scaling-nonscaling transition (SNST) is revealed. For three-dimensional (3D) strongly localized systems the exponent lies between -1 and 1, and surprisingly is quantized (x ≈ 0.08 n). This poses a serious theoretical challenge. Various results are compared with predictions of the existing theories.

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Nonlinear dc conductivity in disordered metals near the metal-insulator transition

Cited by 10 publications

References 15 publications

Path-integral approach to strongly nonlinear composites

Path-integral approach to strongly nonlinear composites

Tuning the Conductivity by Disorder and Electric Field Near the Metal–Insulator Transition

Universal scaling in disordered systems and nonuniversal exponents

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