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Water, honey and electrons – evidence for electronic hydrodynamics in naturally occurring materials

Physikalisches Kolloquium


Andrew Mackenzie


26.01.2018 15:45


Otto Lehmann Lecture Hall, Bldg. 30.22, KIT Campus South


Max Planck Institute for Chemical Physics of Solids, Dresden


Prof. Dr. Jörg Schmalian


Electrical transport in solids is almost always analysed using an approximation in
which all scattering is assumed to relax the momentum of the electrons. Although
this can be justified in the vast majority of cases, because the electrons are moving
in a lattice to which momentum is efficiently transferred, recent measurements by
several groups give evidence that it is not always true. In ultra-pure systems with
extremely long mean free paths, the momentum-conserving collisions that are
ignored in standard theory can become more rapid than the momentum-relaxing
ones. In this limit, the electronic flow moves into a hydrodynamic regime in which
the electron fluid’s viscosity dominates the resistance measured in flow through
constrained channels. Although not very well known by people working on bulk
materials, the study of such effects goes back over fifty years in the theoretical
literature and over twenty years in experiments on high purity two-dimensional
electron gases. I will try to review the history of the field, then describe new
experiments on PdCoO2 and graphene, and finally make some comments about
extending the investigation to other systems.