50 research outputs found
Inhomogeneous and nonstationary Hall states of the CDW with quantized normal carriers
We suggest a theory for a deformable and sliding charge density wave (CDW) in
the Hall bar geometry for the quantum limit when the carriers in remnant small
pockets are concentrated at lowest Landau levels (LL) forming a fractionally
() filled quantum Hall state. The gigantic polarizability of the CDW
allows for a strong redistribution of electronic densities up to a complete
charge segregation when all carriers occupy, with the maximum filling, a
fraction of the chain length - thus forming the integer quantum Hall
state, while leaving the fraction of the chain length unoccupied. The
electric field in charged regions easily exceeds the pinning threshold of the
CDW, then the depinning propagates into the nominally pinned central region via
sharp domain walls. Resulting picture is that of compensated collective and
normal pulsing counter-currents driven by the Hall voltage. This scenario is
illustrated by numerical modeling for nonstationary distributions of the
current and the electric field. This picture can interpret experiments in
mesa-junctions showing depinning by the Hall voltage and the generation of
voltage-controlled high frequency oscillations (Yu.I. Latyshev, P. Monceau,
A.A. Sinchenko, et al, presented at ECRYS-2011, unpublished).Comment: After International School - Workshop on Electronic Crystals:
ECRYS-201
From chiral anomaly to two-fluid hydrodynamics for electronic vortices
Many recent experiments addressed manifestations of electronic crystals,
particularly the charge density waves, in nano-junctions, under electric field
effect, at high magnetic fields, together with real space visualizations by STM
and micro X-ray diffraction. This activity returns the interest to stationary
or transient states with static and dynamic topologically nontrivial
configurations: electronic vortices as dislocations, instantons as phase slip
centers, and ensembles of microscopic solitons. Describing and modeling these
states and processes calls for an efficient phenomenological theory which
should take into account the degenerate order parameter, various kinds of
normal carriers and the electric field. Here we notice that the commonly
employed time-depend Ginzburg-Landau approach suffers with violation of the
charge conservation law resulting in unphysical generation of particles which
is particularly strong for nucleating or moving electronic vortices. We present
a consistent theory which exploits the chiral transformations taking into
account the principle contribution of the fermionic chiral anomaly to the
effective action. The resulting equations clarify partitions of charges,
currents and rigidity among subsystems of the condensate and normal carriers.
On this basis we perform the numerical modeling of a spontaneously generated
coherent sequence of phase slips - the space-time vortices - serving for the
conversion among the injected normal current and the collective one