21.04.21 - Suvendu Mandal "Persistent correlations in colloidal suspensions"

 

 

Particles experiencing Brownian dynamics are essentially ruled by an environment of noise. Consequently, Brownian particles exhibit random motion even without interaction with other particles. This has so far prevented the detection of crucial effects caused by the interaction of particles: The interaction effect may simply be smaller than the surrounding noise. One such effect is the detection of repeated encounters among the same particles. A similar effect for the diffusion of momentum within noise-free Newtonian motion was discovered by Alder and Wainwright in 1967 [1,2]. The limitation in the case of Brownian motion has now been overcome by a noise-cancellation algorithm and the mentioned memory emerges in the derivative of the time-dependent diffusion coefficient as the sought-after long time tail [3]. At small packing fractions, the simulations fully agree with the analytic low-density prediction, yet the amplitude of the tail becomes dramatically suppressed as the packing fraction is increased. The mode-coupling theory of the glass transition provides a qualitative explanation for the strong variation in terms of the static compressibility as well as the slowing down of the structural relaxation.

 

References.

[1] B. J. Alder and T. E. Wainwright, Phys. Rev. Lett. 18, 988 (1967).

[2] B. J. Alder and T. E. Wainwright, Phys. Rev. A 1, 18 (1970).

[3] S. Mandal, L. Schrack, H. Löwen, M. Sperl, and T. Franosch, Phys. Rev. Lett. 123 (16), 168001, 2019.