499 research outputs found
Realization of a two-channel Kondo model with Josephson junction networks
We show that- in the quantum regime- a Josephson junction rhombi chain (i.e.
a Josephson junction chain made by rhombi formed by joining 4 Josephson
junctions) may be effectively mapped onto a quantum Hamiltonian describing
Ising spins in a transverse magnetic field with open boundary conditions. Then,
we elucidate how a Y-shaped network fabricated with 3 Josephson Junction Rhombi
chains may be used as a quantum device realizing the two channel Kondo model
recently proposed by Tsvelik. We point out that the emergence of a 2 channel
Kondo effect in this superconducting network may be probed through the
measurement of a pertinent Josephson current.Comment: 5 pages, 4 figures. To appear in EP
Hamiltonian theory of the strongly-coupled limit of the Kondo problem in the overscreened case
By properly generalizing Nozie`res' Fermi liquid theory, we construct an
Hamiltonian approach to the scattering of conduction electrons off a spin-1/2
impurity in the ovescreneed Kondo regime, as T -> 0. We derive the S-matrix at
the interacting fixed point, and the corresponding phase shifts, together with
leading energy corrections to the unitary limit. We apply our results to obtain
the low-temperature dependence of the 2-channel Kondo conductance, and we
relate it to possible transport experiments in a Quantum DotComment: 22 pages, 1 figur
Junction of three off-critical quantum Ising chains and two-channel Kondo effect in a superconductor
We show that a junction of three off-critical quantum Ising chains can be
regarded as a quantum spin chain realization of the two-channel spin-1/2
overscreened Kondo effect with two superconducting leads. We prove that, as
long as the Kondo temperature is larger than the superconducting gap, the
equivalent Kondo model flows towards the 2 channel Kondo fixed point. We argue
that our system provides the first controlled realization of 2 channel Kondo
effect with superconducting leads. This, besides its the theoretical interest,
is of importance for potential applications to a number of context, including
the analysis of the quantum entanglement properties of a Kondo system.Comment: 14 pages, 4 .eps figure
Current transport properties and phase diagram of a Kitaev chain with long-range pairing
We describe a method to probe the quantum phase transition between the
short-range topological phase and the long-range topological phase in the
superconducting Kitaev chain with long-range pairing, both exhibiting subgap
modes localized at the edges. The method relies on the effects of the finite
mass of the subgap edge modes in the long-range regime (which survives in the
thermodynamic limit) on the single-particle scattering coefficients through the
chain connected to two normal leads. Specifically, we show that, when the leads
are biased at a voltage V with respect to the superconducting chain, the Fano
factor is either zero (in the short-range correlated phase) or 2e (in the
long-range correlated phase). As a result, we find that the Fano factor works
as a directly measurable quantity to probe the quantum phase transition between
the two phases. In addition, we note a remarkable "critical fractionalization
effect" in the Fano factor, which is exactly equal to e along the quantum
critical line. Finally, we note that a dual implementation of our proposed
device makes it suitable as a generator of large-distance entangled
two-particle states.Comment: 24 pages, 8 .eps figures Published versio
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