title: Connecting structure, dynamics and viscosity in sheared soft colloidal liquids: a medley of anisotropic fluctuations.
abstract: Structural distortion and relaxation are central to any liquid flow. Their full understanding requires simultaneous probing of the mechanical as well as structural and dynamical response. We provide the first full dynamical measurement of the transient structure using combined coherent X-ray scattering and rheology on electrostatically interacting colloidal fluids. We find a stress overshoot during the start-up of shear which is due to the strong anisotropic overstretching and compression of nearest-neighbor distances. The rheological response is reflected in uncorrelated entropy-driven intensity fluctuations. While the structural distortion under steady shear is well described by Smoluchowski theory, we find an increase of the particle dynamics beyond the trivial contribution of flow. After the cessation of shear, the full fluid microstructure and dynamics are restored, both on the structural relaxation timescale. We thus find unique structure-dynamics relations in liquid flow, responsible for the macroscopic rheological behavior of the system.
authors.affiliation: Max Planck Institute for the Structure and Dynamics of Matter, CFEL, Luruper Chaussee 149, 22761 Hamburg, Germany. fabian.westermeier@mpsd.mpg.de.
authors.forename: Fabian
authors.initials: F
authors.lastname: Westermeier
authors.affiliation: Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Pennicard
authors.affiliation: Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Hirsemann
authors.affiliation: Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK.
authors.forename: Ulrich H
authors.initials: UH
authors.lastname: Wagner
authors.affiliation: Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK.
authors.forename: Christoph
authors.initials: C
authors.lastname: Rau
authors.affiliation: Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Graafsma
authors.affiliation: Van der Waals-Zeeman Institute, University of Amsterdam, POSTBUS 94485, 1090 GL Amsterdam, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Schall
authors.affiliation: Forschungszentrum Jülich, Institute of Complex Systems (ICS-3), 52425 Jülich, Germany. p.lettinga@fz-juelich.de.
authors.forename: M Paul
authors.initials: MP
authors.lastname: Lettinga
authors.affiliation: Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Struth