1,580 research outputs found
Hall resistivity of granular metals
We calculate the Hall conductivity \sig_{xy} and resistivity of
a granular system at large tunneling conductance . We show that in
the absence of Coulomb interaction the Hall resistivity depends neither on the
tunneling conductance nor on the intragrain disorder and is given by the
classical formula , where differs from the carrier
density inside the grains by a numerical coefficient determined by the
shape of the grains. The Coulomb interaction gives rise to logarithmic in
temperature correction to in the range \Ga \lesssim T \lesssim
\min(g_T E_c,\ETh), where \Ga is the tunneling escape rate, is the
charging energy and \ETh is the Thouless energy of the grain.Comment: 4 pages, 1 figur
Zero bias anomaly in a two dimensional granular insulator
We compare tunneling density of states (TDOS) into two ultrathin Ag films,
one uniform and one granular, for different degrees of disorder. The uniform
film shows a crossover from Altshuler-Aronov (AA) zero bias anomaly to Efros
Shklovskii (ES) like Coulomb gap as the disorder is increased. The granular
film, on the other hand, exhibits AA behavior even deeply in the insulating
regime. We analyze the data and find that granularity introduces a new regime
for the TDOS. While the conductivity is dominated by hopping between clusters
of grains and is thus insulating, the TDOS probes the properties of an
individual cluster which is "metallic".Comment: 4 pages, 4 figure
Effects of two dimensional plasmons on the tunneling density of states
We show that gapless plasmons lead to a universal
correction to the tunneling
density of states of a clean two dimensional Coulomb interacting electron gas.
We also discuss a counterpart of this effect in the "composite fermion metal"
which forms in the presence of a quantizing perpendicular magnetic field
corresponding to the half-filled Landau level. We argue that the latter
phenomenon might be relevant for deviations from a simple scaling observed by
A.Chang et al in the tunneling characteristics of Quantum Hall liquids.Comment: 12 pages, Latex, NORDITA repor
On dual canonical bases
The dual basis of the canonical basis of the modified quantized enveloping
algebra is studied, in particular for type . The construction of a basis for
the coordinate algebra of the quantum matrices is appropriate for
the study the multiplicative property. It is shown that this basis is invariant
under multiplication by certain quantum minors including the quantum
determinant. Then a basis of quantum SL(n) is obtained by setting the quantum
determinant to one. This basis turns out to be equivalent to the dual canonical
basis
Coherent and incoherent pumping of electrons in double quantum dots
We propose a new mode of operation of an electron pump consisting of two
weakly coupled quantum dots connected to reservoirs. An electron can be
transferred within the device at zero bias voltage when it is subjected to
electromagnetic radiation, thereby exciting the double dot. The excited state
can decay by transferring charge from one lead and to the other lead in one
direction. Depending on the energies of the intermediate states in the pumping
cycle, which are controlled by the gate voltages, this transport is either
incoherent via well-known sequential tunneling processes, or coherent via a
inelastic co-tunneling process. The latter novel mode of operation is possible
only when interdot Coulomb charging is important. The D.C. transport through
the system can be controlled by the frequency of the applied radiation. We
concentrate on the resonant case, when the frequency matches the energy
difference for exciting an electron from one dot into the other. The resonant
peaks in the pumping current should be experimentally observable. We have
developed a density matrix approach which describes the dynamics of the system
on timescales much larger than the period of the applied irradiation. In
contrast to previous works we additionally consider the case of slow modulation
of the irradiation amplitude. Harmonic modulation produces additional sidepeaks
in the photoresponse, and pulsed modulation can be used to resolve the Rabi
frequency in the time-averaged current.Comment: 5 pages, 6 figures. This is an extension of cond-mat/9707310 "A
coherent double-quantum-dot electron pump" This version has been accepted for
publication in Phys. Rev. B. Changes: Added references. Corrected typos.
Changed content mainly the introduction. Regime of device operation is now
specified more precisely. A stability diagram has been added as a figure has
been adde
Frequency dispersion of photon-assisted shot noise in mesoscopic conductors
We calculate the low-frequency current noise for AC biased mesoscopic chaotic
cavities and diffusive wires. Contrary to what happens for the admittance, the
frequency dispersion is not dominated by the electric response time (the "RC"
time of the circuit), but by the time that electrons need to diffuse through
the structure (dwell time or diffusion time). Frequency dispersion of noise
stems from fluctuations of the Fermi distribution function that preserve charge
neutrality. Our predictions can be verified with present experimental
technology.Comment: 5 pages, 3 Figure
Full counting statistics of Luttinger liquid conductor
Non-equilibrium bosonization technique is used to study current fluctuations
of interacting electrons in a single-channel quantum wire representing a
Luttinger liquid (LL) conductor. An exact expression for the full counting
statistics of the transmitted charge is derived. It is given by Fredholm
determinant of the counting operator with a time dependent scattering phase.
The result has a form of counting statistics of non-interacting particles with
fractional charges, induced by scattering off the boundaries between the LL
wire and the non-interacting leads.Comment: 5 pages, 2 figure
Statistics of Transmission Eigenvalues for a Disordered Quantum Point Contact
We study the distribution of transmission eigenvalues of a quantum point
contact with nearby impurities. In the semi-classical case (the chemical
potential lies at the conductance plateau) we find that the transmission
properties of this system are obtained from the ensemble of Gaussian random
reflection matrices. The distribution only depends on the number of open
transport channels and the average reflection eigenvalue and crosses over from
the Poissonian for one open channel to the form predicted by the circuit theory
in the limit of large number of open channels.Comment: 8 pages, 3 figure
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