65 research outputs found
Creation and Manipulation of Anyons in the Kitaev Model
We analyze the effect of local spin operators in the Kitaev model on the
honeycomb lattice. We show, in perturbation around the isolated-dimer limit,
that they create Abelian anyons together with fermionic excitations which are
likely to play a role in experiments. We derive the explicit form of the
operators creating and moving Abelian anyons without creating fermions and show
that it involves multi-spin operations. Finally, the important experimental
constraints stemming from our results are discussed.Comment: 4 pages, 3 figures, published versio
Quantum phase transitions in fully connected spin models: an entanglement perspective
We consider a set of fully connected spins models that display first- or
second-order transitions and for which we compute the ground-state entanglement
in the thermodynamical limit. We analyze several entanglement measures
(concurrence, R\'enyi entropy, and negativity), and show that, in general,
discontinuous transitions lead to a jump of these quantities at the transition
point. Interestingly, we also find examples where this is not the case.Comment: 9 pages, 7 figures, published versio
Finite-size scaling exponents and entanglement in the two-level BCS model
We analyze the finite-size properties of the two-level BCS model. Using the
continuous unitary transformation technique, we show that nontrivial scaling
exponents arise at the quantum critical point for various observables such as
the magnetization or the spin-spin correlation functions. We also discuss the
entanglement properties of the ground state through the concurrence which
appears to be singular at the transition.Comment: 4 pages, 3 figures, published versio
Quantum wire networks with local Z2 symmetry
For a large class of networks made of connected loops, in the presence of an
external magnetic field of half flux quantum per loop, we show the existence of
a large local symmetry group, generated by simultaneous flips of the electronic
current in all the loops adjacent to a given node. Using an ultra-localized
single particle basis adapted to this local Z_2 symmetry, we show that it is
preserved by a large class of interaction potentials. As a main physical
consequence, the only allowed tunneling processes in such networks are induced
by electron-electron interactions and involve a simultaneous hop of two
electrons. Using a mean-field picture and then a more systematic
renormalization-group treatment, we show that these pair hopping processes do
not generate a superconducting instability, but they destroy the Luttinger
liquid behavior in the links, giving rise at low energy to a strongly
correlated spin-density-wave state.Comment: 16 pages, 9 figures, v.2 section IV D added,accepted for publication
in PR
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