Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 74: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 74.11: Talk

Wednesday, April 2, 2014, 17:45–18:00, BEY 81

π Fluxes near the Edge of a Topological Insulator: Kondo Screening of a Soliton — •Manuel Weber, Martin Hohenadler, and Fakher F. Assaad — Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

The insertion of a π flux into a quantum spin Hall insulator creates four spin-charge separated states: the two chargeons with Q=±1 and the two spinons with S_z=±1/2. In the presence of repulsive Coulomb interactions the charged states are gapped out and a local moment is formed. For both free and interacting systems the fluxons lead to a characteristic Curie law in the magnetic susceptibility. We consider the Kane-Mele-Hubbard model on a ribbon with zigzag edges to show that the spinon can be screened by the edge states of a quantum spin Hall insulator. At U=0 their hybridization is dominated by the extent of the edge states, which becomes larger with increasing spin-orbit coupling λ. As the fluxons are exponentially localized, it is sufficient to include Hubbard interactions only at lattice sites directly around the π flux. We have extended the CTQMC method by global susceptibility measurements that reproduce the Curie law of a free π flux even for this reduced interacting system. When the spinon is screened by the edge states, we observe deviations from the Curie law for different U and λ that follow the universal behavior obtained from a data collapse. Moreover, at low temperatures a Kondo resonance arises in the spectral function between two low-lying Hubbard peaks.