Hydrodynamic flow of electrons in clean conductors

4 problems

• Boundary slip length of viscous electron flow at sample edges

  Open

  How fast a viscous liquid moves at a wall sets the shape of its flow in a channel. For electron liquids this boundary condition depends on how electrons scatter off sample edges and is poorly known.

• Shear viscosity of the graphene Dirac fluid near charge neutrality

  Partially resolved

  When graphene has equal numbers of electrons and holes, its carriers form a nearly ideal relativistic fluid. Its viscosity has been estimated only indirectly, so how close it comes to a conjectured quantum lower limit is not settled.

• Is the Dyakonov-Shur plasma-wave instability observable in a real device

  Open

  Theory from 1993 predicts that a steady current through a gated two-dimensional electron channel with different conditions at its two ends spontaneously turns into terahertz oscillations. A clear observation of this self-generated oscillation has not been established.

• Do two-dimensional Fermi liquids show odd-even tomographic relaxation

  Open

  In two dimensions, theory predicts that distortions of the electrons' momentum distribution with odd symmetry decay much more slowly than even ones. This would give a distinct transport regime between ballistic and viscous flow.