10 research outputs found
A conformal field theory description of magnetic flux fractionalization in Josephson junction ladders
We show how the recently proposed effective theory for a Quantum Hall system
at "paired states" filling v=1 (Mod. Phys. Lett. A 15 (2000) 1679; Nucl. Phys.
B641 (2002) 547), the twisted model (TM), well adapts to describe the
phenomenology of Josephson Junction ladders (JJL) in the presence of defects.
In particular it is shown how naturally the phenomenon of flux
fractionalization takes place in such a description and its relation with the
discrete symmetries present in the TM. Furthermore we focus on closed
geometries, which enable us to analyze the topological properties of the ground
state of the system in relation to the presence of half flux quanta.Comment: 16 pages, 2 figure, Latex, revised versio
New Results on the Phase Diagram of the FFXY Model: A Twisted CFT Approach
The issue of the number, nature and sequence of phase transitions in the
fully frustrated XY (FFXY) model is a highly non trivial one due to the complex
interplay between its continuous and discrete degrees of freedom. In this
contribution we attack such a problem by means of a twisted conformal field
theory (CFT) approach and show how it gives rise to the U (1)
symmetry and to the whole spectrum of excitations of the FFXY model.Comment: 7 pages; talk given by G. Niccoli at "Path Integrals - New Trends and
Perspectives International Conference", Max-Planck-Institut, Dresden,
Germany, September 23 - 28, 200
Topological order in Josephson junction ladders with Mobius boundary conditions
We propose a CFT description for a closed one-dimensional fully frustrated
ladder of quantum Josephson junctions with Mobius boundary conditions, in
particular we show how such a system can develop topological order. Such a
property is crucial for its implementation as a "protected" solid state qubit.Comment: 14 pages, 3 figures, to appear in JSTA
Topologically protected qubits as minimal Josephson junction arrays with non trivial boundary conditions: a proposal
A general CFT model for antiferromagnetic spin-1/2 ladders with Mobius boundary conditions
We show how the low-energy properties of the 2-leg XXZ spin-1/2 ladders with
general anisotropy parameter on closed geometries can be accounted
for in the framework of the m-reduction procedure developed in [1]. In the
limit of quasi-decoupled chains, a conformal field theory (CFT) with central
charge c=2 is derived and its ability to describe the model with different
boundary conditions is shown. Special emphasis is given to the Mobius boundary
conditions which generate a topological defect corresponding to non trivial
single-spinon excitations. Then, in the case of the 2-leg XXX ladders we
discuss in detail the role of various perturbations in determining the
renormalization group flow starting from the ultraviolet (UV) critical point
with c=2.Comment: 23 pages, 5 figures; J. Stat. Mech.: Theory Exp. (2008), in prin