Kondo screening of spincharge separated fluxons by a helical liquid
Abstract
The insertion of a magnetic π flux into a quantum spin Hall insulator creates four localized, spincharge separated states: the charge and spin fluxons with either charge Q =±1 or spin S_{z}=±1/2, respectively. In the presence of repulsive Coulomb interactions, the charged states are gapped out and a local moment is formed. We consider the KaneMeleHubbard model on a ribbon with zigzag edges to construct an impurity model where the spin fluxon is screened by the helical edge liquid. In the noninteracting model, the hybridization between fluxon and edge states is dominated by the extent of the latter. It becomes larger with increasing spinorbit coupling λ but only has nonzero values for even distances between the π flux and the edge. For the interacting system, we use the continuoustime quantum Monte Carlo method, which we have extended by global susceptibility measurements to reproduce the characteristic Curie law of the spin fluxon. However, due to the finite extent of the fluxons, the local moment is formed at rather low energies. The screening of the spin fluxon leads to deviations from the Curie law that follow the universal behavior obtained from a data collapse. Additionally, the Kondo resonance arises in the local spectral function between the two lowlying Hubbard peaks.
 Publication:

Physical Review B
 Pub Date:
 May 2014
 DOI:
 10.1103/PhysRevB.89.205125
 arXiv:
 arXiv:1403.6372
 Bibcode:
 2014PhRvB..89t5125W
 Keywords:

 71.10.Pm;
 73.43.f;
 72.10.Fk;
 02.70.Uu;
 Fermions in reduced dimensions;
 Quantum Hall effects;
 Scattering by point defects dislocations surfaces and other imperfections;
 Applications of Monte Carlo methods;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 10 pages, 9 figures