1201.6668 (Abolfazl Bayat et al.)

Uncovering real-space properties of the two-impurity Kondo model through
quantum entanglement    [PDF]

Abolfazl Bayat, Sougato Bose, Pasquale Sodano, Henrik Johannesson

We propose that real-space properties of the two-impurity Kondo model can be
obtained from an effective spin model where two single-impurity Kondo spin
chains are joined via an RKKY interaction between the two impurity spins. We
then use a DMRG approach, valid in all ranges of parameters, to study its
features using two complementary quantum-entanglement measures, the negativity
and the von Neumann entropy. This non-perturbative approach enables us to
uncover the precise dependence of the spatial extent of the Kondo screening
cloud with the Kondo and RKKY couplings. Our results reveal an exponential
suppression of the Kondo temperature with the size of the effective impurity
spin in the limit of large ferromagnetic RKKY coupling, a striking display of
"Kondo resonance narrowing" in the two-impurity Kondo model. We also show how
the antiferromagnetic RKKY interaction produces an effective decoupling of the
impurities from the bulk already for intermediate strengths of this
interaction, and, furthermore, exhibit how the non-Fermi liquid quantum
critical point is signaled in the quantum entanglement between various parts of
the system.

View original: http://arxiv.org/abs/1201.6668