The strong spin-orbit coupling, unusual spectrum, and the quantum criticality make the systems with the Dirac hamiltonian particularly interesting objects for studying.
Since the discovery of graphene, the basic properties of the Dirac hamiltonian were extensively studied. Nevertheless, the description of the inhomogeneous and non-equilibrium dynamics in the presence of interactions is still a challenging problem. Traditionally, to solve such problems the semiclassical approach is used. In the presence of strong interactions with some internal symmetries also the hydrodynamical approach is an adequate way to describe the non-equilibrium system’s behaviour.
We investigated the Boltzmann equation for the HgTe slabs, describing the transport in the presence of e-e interaction leading to Gurzhi effect, which can be used as a signature of the hydrodynamic transport. We also investigated the spin-momentum locking ansatz for the kinetic equation and pointed out that taking into account of this mode softening is absolutely crucial for the spin current definition in the 2D Dirac system.