1,254 research outputs found

### Spin-dependent transport through a chiral molecule in the presence of spin-orbit interaction and non-unitary effects

Recent experiments have demonstrated the efficacy of chiral helically shaped
molecules in polarizing the scattered electron spin, an effect termed as
chiral-induced spin selectivity (CISS). Here we solve a simple tight-binding
model for electron transport through a single helical molecule, with spin-orbit
interactions on the bonds along the helix. Quantum interference is introduced
via additional electron hopping between neighboring sites in the direction of
the helix axis. When the helix is connected to two one-dimensional single-mode
leads, time-reversal symmetry prevents spin polarization of the outgoing
electrons. One possible way to retrieve such a polarization is to allow leakage
of electrons from the helix to the environment, via additional outgoing leads.
Technically, the leakage generates complex site self-energies, which break
unitarity. As a result, the electron waves in the helix become evanescent, with
different decay lengths for different spin polarizations, yielding a net spin
polarization of the outgoing electrons, which increases with the length of the
helix (as observed experimentally). A maximal polarization can be measured at a
finite angle away from the helix axis.Comment: 12 pages, 5 figure

### Fluctuation Theorem in a Quantum-Dot Aharonov-Bohm Interferometer

In the present study, we investigate the full counting statistics in a
two-terminal Aharonov-Bohm interferometer embedded with an interacting quantum
dot. We introduce a novel saddle-point solution for a cumulant-generating
function, which satisfies the fluctuation theorem and accounts for the
interaction in the mean-field level approximation. Nonlinear transport
coefficients satisfy universal relations imposed by microscopic reversibility,
though the scattering matrix itself is not reversible. The skewness can be
finite even in equilibrium, owing to the interaction and is proportional to the
asymmetric component of nonlinear conductance.Comment: 5 pages, 2 figure

### Full Counting Statistics for a Single-Electron Transistor, Non-equilibrium Effects at Intermediate Conductance

We evaluate the current distribution for a single-electron transistor with
intermediate strength tunnel conductance. Using the Schwinger-Keldysh approach
and the drone (Majorana) fermion representation we account for the
renormalization of system parameters. Nonequilibrium effects induce a lifetime
broadening of the charge-state levels, which suppress large current
fluctuations.Comment: 4 pages, 1 figur

### Full counting statistics of information content

We review connections between the cumulant generating function of full
counting statistics of particle number and the R\'enyi entanglement entropy. We
calculate these quantities based on the fermionic and bosonic path-integral
defined on multiple Keldysh contours. We relate the R\'enyi entropy with the
information generating function, from which the probability distribution
function of self-information is obtained in the nonequilibrium steady state. By
exploiting the distribution, we analyze the information content carried by a
single bosonic particle through a narrow-band quantum communication channel.
The ratio of the self-information content to the number of bosons fluctuates.
For a small boson occupation number, the average and the fluctuation of the
ratio are enhanced.Comment: 16 pages, 5 figure

### Statistics of voltage fluctuations in resistively shunted Josephson junctions

The intrinsic nonlinearity of Josephson junctions converts Gaussian current
noise in the input into non-Gaussian voltage noise in the output. For a
resistively shunted Josephson junction with white input noise we determine
numerically exactly the properties of the few lowest cumulants of the voltage
fluctuations, and we derive analytical expressions for these cumulants in
several important limits. The statistics of the voltage fluctuations is found
to be Gaussian at bias currents well above the Josephson critical current, but
Poissonian at currents below the critical value. In the transition region close
to the critical current the higher-order cumulants oscillate and the voltage
noise is strongly non-Gaussian. For coloured input noise we determine the third
cumulant of the voltage.Comment: 9 pages, 5 figure

### Symmetry in Full Counting Statistics, Fluctuation Theorem, and Relations among Nonlinear Transport Coefficients in the Presence of a Magnetic Field

We study full counting statistics of coherent electron transport through
multi-terminal interacting quantum-dots under a finite magnetic field.
Microscopic reversibility leads to the symmetry of the cumulant generating
function, which generalizes the fluctuation theorem in the context of quantum
transport. Using this symmetry, we derive the Onsager-Casimir relation in the
linear transport regime and universal relations among nonlinear transport
coefficients.Comment: 4.1pages, 1 figur

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