1,681 research outputs found
Stationary transport in mesoscopic hybrid structures with contacts to superconducting and normal wires. A Green's function approach for multiterminal setups
Get PDFWe generalize the representation of the real time Green's functions
introduced by Langreth and Nordlander [Phys. Rev. B 43 2541 (1991)] and Meir
and Wingreen [Phys. Rev. Lett. 68 2512 (1992)] in stationary quantum transport
in order to study problems with hybrid structures containing normal (N) and
superconducting (S) pieces. We illustrate the treatment in a S-N junction under
a stationary bias and investigate in detail the behavior of the equilibrium
currents in a normal ring threaded by a magnetic flux with attached
superconducting wires at equilibrium. We analyze the flux sensitivity of the
Andreev states and we show that their response is equivalent to the one
corresponding to the Cooper pairs with momentum q=0 in an isolated
superconducting ring.Comment: 11 pages, 3 figure
Renormalization of modular invariant Coulomb gas and Sine-Gordon theories, and quantum Hall flow diagram
Full text linkUsing the renormalisation group (RG) we study two dimensional electromagnetic
coulomb gas and extended Sine-Gordon theories invariant under the modular group
SL(2,Z). The flow diagram is established from the scaling equations, and we
derive the critical behaviour at the various transition points of the diagram.
Following proposal for a SL(2,Z) duality between different quantum Hall fluids,
we discuss the analogy between this flow and the global quantum Hall phase
diagram.Comment: 10 pages, 1 EPS figure include
Efficient solutions of self-consistent mean field equations for dewetting and electrostatics in nonuniform liquids
Full text linkWe use a new configuration-based version of linear response theory to
efficiently solve self-consistent mean field equations relating an effective
single particle potential to the induced density. The versatility and accuracy
of the method is illustrated by applications to dewetting of a hard sphere
solute in a Lennard-Jones fluid, the interplay between local hydrogen bond
structure and electrostatics for water confined between two hydrophobic walls,
and to ion pairing in ionic solutions. Simulation time has been reduced by more
than an order of magnitude over previous methods.Comment: Supplementary material included at end of main pape
Influence of the nucleon spectral function in photon and electron induced reactions on nuclei
Full text linkWe study the influence of the nucleon spectral function on eta photo- and
electroproduction on nuclei. Besides kinematical effects due to groundstate
correlations, also a modification of the S11(1535) decay width is taken into
account, which is caused by the possible decay into nucleons with mass smaller
than the pole mass in the medium. Hence, resonances with masses below the free
N eta threshold can contribute to eta production.Comment: 13 pages, 8 figure
Conductivity fluctuations in polymer's networks
Full text linkPolymer's network is treated as an anisotropic fractal with fractional
dimensionality D = 1 + \epsilon close to one. Percolation model on such a
fractal is studied. Using the real space renormalization group approach of
Migdal and Kadanoff we find threshold value and all the critical exponents to
be strongly nonanalytic functions of \epsilon, e.g. the critical exponent of
the conductivity was obtained to be \epsilon^{-2}\exp(-1-1/\epsilon). The main
part of the finite size conductivities distribution function at the threshold
was found to be universal if expressed in terms of the fluctuating variable,
which is proportional to the large power of the conductivity, but with
dimensionally-dependent low-conductivity cut-off. Its reduced central momenta
are of the order of \exp(-1/\epsilon) up to the very high order.Comment: 7 pages, one eps figure, uses epsf style, to be published in Proc. of
LEES-97 (Physica B
Double point contact in Quantum Hall Line Junctions
Full text linkWe show that multiple point contacts on a barrier separating two laterally
coupled quantum Hall fluids induce Aharonov-Bohm (AB) oscillations in the
tunneling conductance. These quantum coherence effects provide new evidence for
the Luttinger liquid behavior of the edge states of quantum Hall fluids. For a
two point contact, we identify coherent and incoherent regimes determined by
the relative magnitude of their separation and the temperature. We analyze both
regimes in the strong and weak tunneling amplitude limits as well as their
temperature dependence. We find that the tunneling conductance should exhibit
AB oscillations in the coherent regime, both at strong and weak tunneling
amplitude with the same period but with different functional form.Comment: 4 pages, 3 figures; new version, edited text, 2 new references;
figure 2 has been edited; new paragraph in page 1 and minor typos have been
correcte
Boltzmann Collision Term
Full text linkWe derive the Boltzmann equation for scalar fields using the
Schwinger-Keldysh formalism. The focus lies on the derivation of the collision
term. We show that the relevant self-energy diagrams have a factorization
property. The collision term assumes the Boltzmann-like form of scattering
probability times statistical factors for those self-energy diagrams which
correspond to tree level scattering processes. Our proof covers scattering
processes with any number of external particles, which come from self-energy
diagrams with any number of loops.Comment: 17 pages, 4 figure
In-Medium Effects in Photo- and Neutrino-Induced Reactions on Nuclei
Get PDFIn this talk various aspects of in-medium behavior of hadrons are discussed
with an emphasis on observable effects. It is stressed that final state
interactions can have a major effect on observables and thus have to be
considered as part of the theory. This is demonstrated with examples from
photo-nucleus and neutrino-nucleus interactions.Comment: Invited talk, given by U. Mosel, at MESON2006, 9-th International
Workshop on Meson Production, Interaction and Decay, June 9-13, 2006, Cracow,
Polan
The "topological" charge for the finite XX quantum chain
Full text linkIt is shown that an operator (in general non-local) commutes with the
Hamiltonian describing the finite XX quantum chain with certain non-diagonal
boundary terms. In the infinite volume limit this operator gives the
"topological" charge.Comment: 5 page
Artificial electric field in Fermi Liquids
Full text linkBased on the Keldysh formalism, we derive an effective Boltzmann equation for
a quasi-particle associated with a particular Fermi surface in an interacting
Fermi liquid. This provides a many-body derivation of Berry curvatures in
electron dynamics with spin-orbit coupling, which has received much attention
in recent years in non-interacting models. As is well-known, the Berry
curvature in momentum space modifies naive band dynamics via an artificial
magnetic field in momentum space. Our Fermi liquid formulation completes the
reinvention of modified band dynamics by introducing in addition an "artificial
electric field", related to Berry curvature in frequency and momentum space. We
show explicitly how the artificial electric field affects the renormalization
factor and transverse conductivity of interacting U(1) Fermi liquids with
non-degenerate bands. Accordingly, we also propose a method of momentum
resolved Berry's curvature detection in terms of angle resolved photoemission
spectroscopy (ARPES)
- …
