21 research outputs found
Coulomb effects in electronic transport
Charge transport in metals and semiconductors is often dominated by electron-impurity and electron–phonon scattering. Coulomb effects could be found in small corrections to the leading behavior, drag effects in specially fabricated samples, compensated semimetals, and hydrodynamic phenomena in ultra-pure materials. In contrast, electrical resistivity in strongly correlated systems is poorly understood. Understanding the fate of electron–phonon scattering in these materials may offer a route towards future advancements
Hydrodynamic approach to two-dimensional electron systems
The last few years have seen an explosion of interest in hydrodynamic effects in interacting electron systems in ultra-pure materials. One such material, graphene, is not only an excellent platform for the experimental realization of the hydrodynamic flow of electrons, but also allows for a controlled derivation of the hydrodynamic equations on the basis of kinetic theory. The resulting hydrodynamic theory of electronic transport in graphene yields quantitative predictions for experimentally relevant quantities, e.g., viscosity, electrical conductivity, etc. Here I review recent theoretical advances in the field, compare the hydrodynamic theory of charge carriers in graphene with relativistic hydrodynamics and recent experiments, and discuss applications of hydrodynamic approach to novel materials beyond graphene
Interference of quantum critical excitations and soft diffusive modes in a disordered antiferromagnetic metal
We study the temperature-dependent quantum correction to conductivity due to
the interplay of spin density fluctuations and weak disorder for a
two-dimensional metal near an antiferromagnetic (AFM) quantum critical point.
AFM spin density fluctuations carry large momenta around the ordering vector
and, at lowest order of the spin-fermion coupling, only scatter
electrons between "hot spots" of the Fermi surface which are connected by
. Earlier, it was seen that the quantum interference between AFM
spin density fluctuations and soft diffusive modes of the disordered metal is
suppressed, a consequence of the large-momentum scattering. The suppression of
this interference results in a non-singular temperature dependence of the
corresponding interaction correction to conductivity. However, at higher order
of the spin-fermion coupling, electrons on the entire Fermi surface can be
scattered successively by two spin density fluctuations and, in total, suffer a
small momentum transfer. This higher-order process can be described by
composite modes which carry small momenta. We show that the interference
between formally subleading composite modes and diffusive modes generates
singular interaction corrections which ultimately dominate over the
non-singular first-order correction at low temperatures. We derive an effective
low-energy theory from the spin-fermion model which includes the
above-mentioned higher-order process implicitly and show that for weak
spin-fermion coupling the small-momentum transfer is mediated by a composite
propagator. Employing the conventional diagrammatic approach to impurity
scattering, we find the correction for
temperatures above an exponentially small crossover scale.Comment: 13 pages, 7 figures. Published versio
Elastic response of the electron fluid in intrinsic graphene: The collisionless regime
The elastic response of an electron fluid at finite frequencies is defined by
the electron viscosity . We determine for graphene
at the charge neutrality point in the collisionless regime, including the
leading corrections due to the electron-electron Coulomb interaction. We find
interaction corrections to that are significantly larger if
compared to the corresponding corrections to the optical conductivity. In
addition, we find comparable contributions to the dynamic momentum flux due to
single-particle and many-particle effects. We also demonstrate that
is directly related to the nonlocal energy-flow response of
graphene at the Dirac point. The viscosity in the collisionless regime is
determined with the help of the strain generators in the Kubo formalism. Here,
the pseudo-spin of graphene describing its two sublattices plays an important
role in obtaining a viscosity tensor that fulfills the symmetry properties of a
rotationally symmetric system.Comment: 18 pages, 5 figure
Electronic viscosity and energy relaxation in neutral graphene
We explore hydrodynamics of Dirac fermions in neutral graphene in the Corbino geometry. In the absence of magnetic field, the bulk Ohmic charge flow and the hydrodynamic energy flow are decoupled. However, the energy flow does affect the overall resistance of the system through viscous dissipation and energy relaxation that has to be compensated by the work done by the current source. Solving the hydrodynamic equations, we find that local temperature and electric potential are discontinuous at the interfaces with the leads as well as the device resistance and argue that this makes Corbino geometry a feasible choice for an experimental observation of the Dirac fluid
Corbino magnetoresistance in neutral graphene
We explore the magnetohydrodynamics of Dirac fermions in neutral graphene in
the Corbino geometry. Based on the fully consistent hydrodynamic description
derived from a microscopic framework and taking into account all peculiarities
of graphene-specific hydrodynamics, we report the results of a comprehensive
study of the interplay of viscosity, disorder-induced scattering,
recombination, energy relaxation, and interface-induced dissipation. In the
clean limit, magnetoresistance of a Corbino sample is determined by viscosity.
Hence the Corbino geometry could be used to measure the viscosity coefficient
in neutral graphene.Comment: 13 pages, 11 figure