36 research outputs found
Full Counting Statistics of Superconductor--Normal-Metal Heterostructures
The article develops a powerful theoretical tool to obtain the full counting
statistics. By a slight extension of the standard Keldysh method we can access
immediately all correlation functions of the current operator. Embedded in a
quantum generalization of the circuit theory of electronic transport, we are
able to study the full counting statistics of a large class of two-terminal
contacts and multi-terminal structures, containing superconductors and normal
metals as elements. The practical use of the method is demonstrated in many
examples.Comment: 35 pages, contribution to "Quantum Noise", ed. by Yu.V. Nazarov and
Ya.M. Blanter, minor changes in text, references adde
Shot noise in mesoscopic systems
This is a review of shot noise, the time-dependent fluctuations in the
electrical current due to the discreteness of the electron charge, in small
conductors. The shot-noise power can be smaller than that of a Poisson process
as a result of correlations in the electron transmission imposed by the Pauli
principle. This suppression takes on simple universal values in a symmetric
double-barrier junction (suppression factor 1/2), a disordered metal (factor
1/3), and a chaotic cavity (factor 1/4). Loss of phase coherence has no effect
on this shot-noise suppression, while thermalization of the electrons due to
electron-electron scattering increases the shot noise slightly. Sub-Poissonian
shot noise has been observed experimentally. So far unobserved phenomena
involve the interplay of shot noise with the Aharonov-Bohm effect, Andreev
reflection, and the fractional quantum Hall effect.Comment: 37 pages, Latex, 10 figures (eps). To be published in "Mesoscopic
Electron Transport," edited by L. P. Kouwenhoven, G. Schoen, and L. L. Sohn,
NATO ASI Series E (Kluwer Academic Publishing, Dordrecht
Towards identification of a non-abelian state: observation of a quarter of electron charge at quantum Hall state
The fractional quantum Hall effect, where plateaus in the Hall resistance at
values of coexist with zeros in the longitudinal resistance, results from
electron correlations in two dimensions under a strong magnetic field. Current
flows along the edges carried by charged excitations (quasi particles) whose
charge is a fraction of the electron charge. While earlier research
concentrated on odd denominator fractional values of , the observation of
the even denominator state sparked a vast interest. This state is
conjectured to be characterized by quasiparticles of charge e/4, whose
statistics is non-abelian. In other words, interchanging of two quasi particles
may modify the state of the system to an orthogonal one, and does not just add
a phase as in for fermions or bosons. As such, these quasiparticles may be
useful for the construction of a topological quantum computer. Here we report
data of shot noise generated by partitioning edge currents in the
state, consistent with the charge of the quasiparticle being e/4, and
inconsistent with other potentially possible values, such as e/2 and e. While
not proving the non-abelian nature of the state, this observation is
the first step toward a full understanding of these new fractional charges
Keldysh technique and non-linear sigma-model: basic principles and applications
The purpose of this review is to provide a comprehensive pedagogical
introduction into Keldysh technique for interacting out-of-equilibrium
fermionic and bosonic systems. The emphasis is placed on a functional integral
representation of underlying microscopic models. A large part of the review is
devoted to derivation and applications of the non-linear sigma-model for
disordered metals and superconductors. We discuss such topics as transport
properties, mesoscopic effects, counting statistics, interaction corrections,
kinetic equation, etc. The sections devoted to disordered superconductors
include Usadel equation, fluctuation corrections, time-dependent
Ginzburg-Landau theory, proximity and Josephson effects, etc. (This review is a
substantial extension of arXiv:cond-mat/0412296.)Comment: Review: 103 pages, 19 figure