Speaker
Description
We study the roles of Coulomb interactions in transport properties of interacting Dirac electrons in two-dimensions. We study it from a weak-coupling and a strong-coupling perspective. We demonstrate that long-range Coulomb interactions play two independent roles. (i) In the weak-coupling analysis, they provide the inelastic and momentum-conserving scattering mechanism that leads to fast local equilibration which is a prerequisite for electron hydrodynamics. (ii) In the strong-coupling analysis, they facilitate the emergence of collective excitations, plasmons, that contribute to transport properties on equal footing with electrons. While the electron hydrodynamics has been studied intensively for many years, the role of plasmons in the transport properties of Dirac systems receives much less attention. In this work, we show that plasmons make a sizeable contribution to the thermal conductivity. While the increase at the Dirac point is moderate, it becomes large towards larger doping. We suspect, that this is a generic feature of ultraclean two-dimensional electronic systems, also applicable to degenerate systems. We suggested that this effect can be experimentally observed, for example, in graphene of which the effective fine-structure constant characterizing the strength of the Coulomb interactions is of order 1.
