Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Low-dimensional Systems - Models II

TT 33.1: Vortrag

Freitag, 30. März 2007, 10:15–10:30, H18

String order: a common (and fragile) characterization of 1D insulators — •Fabrizio Anfuso and Achim Rosch — Institute of Theoretical Physics, University of Cologne

The ground-state of spin-1 Haldane chains is characterized by the so-called string order. We show that the same hidden order is also present in ordinary one-dimensional band insulators. We construct a family of Hamiltonians which connects adiabatically band insulators to two topologically non-equivalent spin models, the Haldane chain and the antiferromagnetic spin-1/2 ladder. We observe that localized spin-1/2 edge-state characteristic of spin-1 chains is smoothly connected to a surface-bound state of band insulators and its emergence is not related to any bulk phase transition. Furthermore, we show that the string order is absent in any dimensions higher than one and we discuss the similar fate of other non-local hidden orders.