7,552 research outputs found
Towards the electron EDM search: Theoretical study of HfF+
We report first ab initio relativistic correlation calculations of potential
curves for ten low-lying electronic states, effective electric field on the
electron and hyperfine constants for the ^3\Delta_1 state of cation of a heavy
transition metal fluoride, HfF^+, that is suggested to be used as the working
state in experiments to search for the electric dipole moment of the electron.
It is shown that HfF^+ has deeply bound ^1\Sigma^+ ground state, its
dissociation energy is D_e=6.4 eV. The ^3\Delta_1 state is obtained to be the
relatively long-lived first excited state lying about 0.2 eV higher. The
calculated effective electric field E_eff=W_d|\Omega| acting on an electron in
this state is 5.84*10^{24}Hz/(e*cm)Comment: 4 page
Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry
Ultra-pure conductors may exhibit hydrodynamic transport where the collective
motion of charge carriers resembles the flow of a viscous fluid. In a confined
geometry (e.g., in ultra-high quality nanostructures) the electronic fluid
assumes a Poiseuille-like flow. Applying an external magnetic field tends to
diminish viscous effects leading to large negative magnetoresistance. In
two-component systems near charge neutrality the hydrodynamic flow of charge
carriers is strongly affected by the mutual friction between the two
constituents. At low fields, the magnetoresistance is negative, however at high
fields the interplay between electron-hole scattering, recombination, and
viscosity results in a dramatic change of the flow profile: the
magnetoresistance changes its sign and eventually becomes linear in very high
fields. This novel non-monotonic magnetoresistance can be used as a fingerprint
to detect viscous flow in two-component conducting systems.Comment: 10 pages, 8 figure
Counterflows in viscous electron-hole fluid
In ultra-pure conductors, collective motion of charge carriers at relatively
high temperatures may become hydrodynamic such that electronic transport may be
described similarly to a viscous flow. In confined geometries (e.g., in
ultra-high quality nanostructures), the resulting flow is Poiseuille-like. When
subjected to a strong external magnetic field, the electric current in
semimetals is pushed out of the bulk of the sample towards the edges. Moreover,
we show that the interplay between viscosity and fast recombination leads to
the appearance of counterflows. The edge currents possess a non-trivial spatial
profile and consist of two stripe-like regions: the outer stripe carrying most
of the current in the direction of the external electric field and the inner
stripe with the counterflow.Comment: 10 pages, 5 figure
L\'evy flights due to anisotropic disorder in graphene
We study transport properties of graphene with anisotropically distributed
on-site impurities (adatoms) that are randomly placed on every third line drawn
along carbon bonds. We show that stripe states characterized by strongly
suppressed back-scattering are formed in this model in the direction of the
lines. The system reveals L\'evy-flight transport in stripe direction such that
the corresponding conductivity increases as the square root of the system
length. Thus, adding this type of disorder to clean graphene near the Dirac
point strongly enhances the conductivity, which is in stark contrast with a
fully random distribution of on-site impurities which leads to Anderson
localization. The effect is demonstrated both by numerical simulations using
the Kwant code and by an analytical theory based on the self-consistent
-matrix approximation.Comment: 11 pages, 6 figure
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