619 research outputs found
Coulomb blockade and Bloch oscillations in superconducting Ti nanowires
Quantum fluctuations in quasi-one-dimensional superconducting channels
leading to spontaneous changes of the phase of the order parameter by ,
alternatively called quantum phase slips (QPS), manifest themselves as the
finite resistance well below the critical temperature of thin superconducting
nanowires and the suppression of persistent currents in tiny superconducting
nanorings. Here we report the experimental evidence that in a current-biased
superconducting nanowire the same QPS process is responsible for the insulating
state -- the Coulomb blockade. When exposed to RF radiation, the internal Bloch
oscillations can be synchronized with the external RF drive leading to
formation of quantized current steps on the I-V characteristic. The effects
originate from the fundamental quantum duality of a Josephson junction and a
superconducting nanowire governed by QPS -- the QPS junction (QPSJ).Comment: 5 pages, 4 figure
On the reflection of magnon bound states
We investigate the reflection of two-particle bound states of a free open
string in the light-cone AdS_5 x S^5 string sigma model, for large angular
momentum J=J_56 and ending on a D7 brane which wraps the entire AdS_5 and a
maximal S^3 of S^5. We use the superspace formalism to analyse fundamental and
two-particle bound states in the cases of supersymmetry-preserving and
broken-supersymmetry boundaries. We find the boundary S-matrices corresponding
to bound states both in the bulk and on the boundary.Comment: 35 pages, v2: few typos and ref corrected, accepted for publication
in JHE
Normal metal - insulator - superconductor interferometer
Hybrid normal metal - insulator - superconductor microstructures suitable for
studying an interference of electrons were fabricated. The structures consist
of a superconducting loop connected to a normal metal electrode through a
tunnel barrier . An optical interferometer with a beam splitter can be
considered as a classical analogue for this system. All measurements were
performed at temperatures well below 1 K. The interference can be observed as
periodic oscillations of the tunnel current (voltage) through the junction at
fixed bias voltage (current) as a function of a perpendicular magnetic field.
The magnitude of the oscillations depends on the bias point. It reaches a
maximum at energy which is close to the superconducting gap and decreases
with an increase of temperature. Surprisingly, the period of the oscillations
in units of magnetic flux is equal neither to nor to
, but significantly exceeds these values for larger loop circumferences.
The origin of the phenomena is not clear.Comment: 11 pages and 8 figure
On Hamiltonian structure of the spin Ruijsenaars-Schneider model
The Hamiltonian structure of spin generalization of the rational
Ruijsenaars-Schneider model is found by using the Hamiltonian reduction
technique. It is shown that the model possesses the current algebra symmetry.
The possibility of generalizing the found Poisson structure to the
trigonometric case is discussed and degeneration to the Euler-Calogero-Moser
system is examined.Comment: latex, 16 pages, references are adde
Microscopic model for multiple flux transitions in mesoscopic superconducting loops
A microscopic model is constructed which is able to describe multiple
magnetic flux transitions as observed in recent ultra-low temperature tunnel
experiments on an aluminum superconducting ring with normal metal - insulator -
superconductor junctions [Phys. Rev. B \textbf{70}, 064514 (2004)]. The unusual
multiple flux quantum transitions are explained by the formation of metastable
states with large vorticity. Essential in our description is the modification
of the pairing potential and the superconducting density of states by a
sub-critical value of the persistent current which modulates the measured
tunnel current. We also speculate on the importance of the injected
non-equilibrium quasiparticles on the stability of these metastable states.Comment: 6 pages, 3 figure
The Zamolodchikov-Faddeev algebra for open strings attached to giant gravitons
We extend the Zamolodchikov-Faddeev algebra for the superstring sigma model
on , which was formulated by Arutyunov, Frolov and
Zamaklar, to the case of open strings attached to maximal giant gravitons,
which was recently considered by Hofman and Maldacena. We obtain boundary
-matrices which satisfy the standard boundary Yang-Baxter equation.Comment: 22 pages, no figure; added a referenc
On correlation functions of operators dual to classical spinning string states
We explore how to compute, classically at strong coupling, correlation
functions of local operators corresponding to classical spinning string states.
The picture we obtain is of `fattened' Witten diagrams, the evaluation of which
turns out to be surprisingly subtle and requires a modification of the naive
classical action due to a necessary projection onto appropriate wave functions.
We examine string solutions which compute the simplest case of a two-point
function and reproduce the right scaling with the anomalous dimensions
corresponding to the energies of the associated spinning string solutions. We
also describe, under some simplifying assumptions, how the spacetime dependence
of a conformal three-point correlation function arises in this setup.Comment: 27 pages, 3 figures; v2: references and comments added
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