Colloids exposed to random potential energy landscapes: From particle number density to particle-potential and particle-particle interactions

Bewerunge, Jörg; Sengupta, Ankush; Capellmann, R. F.; Platten, Florian; Sengupta, Surajit; Egelhaaf, Stefan U.

doi:10.1063/1.4959129

Cited by 13 publications

(28 citation statements)

References 83 publications

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“…(IX. 49) In these expressions, the natural units of length and time, R and τ = R 2 /(2D 0 ), respectively, have been made evident. The time τ merely is the time at which the characteristic lengthscale of free diffusion √ 2D 0 t reaches the correlation length of the disorder.…”

Section: T) (Ix1c)mentioning

confidence: 99%

Dynamics of a noninteracting colloidal fluid in a quenched Gaussian random potential: a time-reversal-symmetry-preserving field-theoretic approach

Kim¹,

Fuchs²,

Krakoviack³

2020

J. Stat. Mech.

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We develop a field-theoretic perturbation method preserving the fluctuation-dissipation relation (FDR) for the dynamics of the density fluctuations of a noninteracting colloidal gas plunged in a quenched Gaussian random field. It is based on an expansion about the Brownian noninteracting gas and can be considered and justified as a low-disorder or high-temperature expansion. The first-order bare theory yields the same memory integral as the mode-coupling theory (MCT) developed for (ideal) fluids in random environments, apart from the bare nature of the correlation functions involved. It predicts an ergodic dynamical behavior for the relaxation of the density fluctuations, in which the memory kernels and correlation functions develop long-time algebraic tails. A FDR-consistent renormalized theory is also constructed from the bare theory.It is shown to display a dynamic ergodic-nonergodic transition similar to the one predicted by the MCT at the level of the density fluctuations, but, at variance with the MCT, the transition does not fully carry over to the self-diffusion, which always reaches normal diffusive behavior at long time, in agreement with known rigorous results. * vincent.krakoviack@ens-lyon.fr 1 arXiv:1909.09386v2 [cond-mat.dis-nn]

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Section: T) (Ix1c)mentioning

confidence: 99%

Dynamics of a noninteracting colloidal fluid in a quenched Gaussian random potential: a time-reversal-symmetry-preserving field-theoretic approach

Kim¹,

Fuchs²,

Krakoviack³

2020

J. Stat. Mech.

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“…Colloidal experiments have been very important for the understanding of the dynamics and phase behavior of twodimensional (2D) systems. Examples are experiments on the nature of the two-stage melting scenario [1][2][3][4][5], the structure and diffusion in 2D fluids [6][7][8][9][10][11][12][13][14][15][16][17][18][19], the diffusion through 2D random energy landscapes and porous media [20][21][22][23][24], or the glass transition in 2D [25][26][27][28][29][30][31][32]. These experimental studies have been performed on well-characterized model systems in a quasi-2D geometry, which is realized by either sedimenting a monolayer of colloidal particles on a glass plate [13][14][15][16][17], confining the particles between closely spaced glass plates [8,9,33,34], or suspending them on the waterair interface of a water drop [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Long-time self-diffusion in quasi-two-dimensional colloidal fluids of paramagnetic particles

et al. 2020

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The effect of hydrodynamic interactions (HI) on the long-time self-diffusion in quasi-two-dimensional fluids of paramagnetic colloidal particles is investigated using a combination of experiments and Brownian dynamics (BD) simulations. In the BD simulations, the direct interactions (DI) between the particles consist of a shortranged repulsive part and a long-ranged part that is proportional to 1/r 3 , with r the interparticle distance. By studying the equation of state, the simulations allow for the identification of the regime where the properties of the fluid are fully controlled by the long-ranged interactions, and the thermodynamic state solely depends on the dimensionless interaction strength. In this regime, the radial distribution functions from the simulations are in quantitative agreement with those from the experiments for different fluid area fractions. This agreement confirms that the DI in the experiments and simulations are identical, which thus allows us to isolate the role of HI, as these are not taken into account in the BD simulations. Experiment and simulation fall onto a master curve with respect to the dependence of D L = D L /(D 0 1/2), with D 0 the self-diffusion coefficient at infinite dilution and D L the long-time self-diffusion coefficient. Our results thus show that, although HI affect the short-time selfdiffusion, for a quasi-two-dimensional system with 1/r 3 long-ranged DI, the reduced quantity D L is effectively not affected by HI. Interestingly, this is in agreement with prior work on quasi-two-dimensional colloidal hard spheres.

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“…1A ; see Materials and Methods for details on the samples and setup). This imposed an external potential on the particles ( 54 ). While the particles explored the speckle pattern, they were observed with an inverted microscope.…”

Section: Resultsmentioning

confidence: 99%

First-passage statistics of colloids on fractals: Theory and experimental realization

et al. 2022

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In nature and technology, particle dynamics frequently occur in complex environments, for example in restricted geometries or crowded media. These dynamics have often been modeled invoking a fractal structure of the medium although the fractal structure was only indirectly inferred through the dynamics. Moreover, systematic studies have not yet been performed. Here, colloidal particles moving in a laser speckle pattern are used as a model system. In this case, the experimental observations can be reliably traced to the fractal structure of the underlying medium with an adjustable fractal dimension. First-passage time statistics reveal that the particles explore the speckle in a self-similar, fractal manner at least over four decades in time and on length scales up to 20 times the particle radius. The requirements for fractal diffusion to be applicable are laid out, and methods to extract the fractal dimension are established.

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Colloids exposed to random potential energy landscapes: From particle number density to particle-potential and particle-particle interactions

Cited by 13 publications

References 83 publications

Dynamics of a noninteracting colloidal fluid in a quenched Gaussian random potential: a time-reversal-symmetry-preserving field-theoretic approach

Dynamics of a noninteracting colloidal fluid in a quenched Gaussian random potential: a time-reversal-symmetry-preserving field-theoretic approach

Long-time self-diffusion in quasi-two-dimensional colloidal fluids of paramagnetic particles

First-passage statistics of colloids on fractals: Theory and experimental realization

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