Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 18: Poster Session: Topological Topics (joint session TT/MA)

TT 18.13: Poster

Montag, 1. April 2019, 15:00–18:30, Poster D

Quantum phase transitions to topological Haldane phases in spin-one chains studied by linked-cluster expansions — •Patrick Adelhardt¹, Julian Gritsch¹, Marvin Hille², David Anselm Reiss¹, and Kai Phillip Schmidt¹ — ¹Institute for Theoretical Physics, FAU Erlangen-Nürnberg, Germany — ²Lehrstuhl für Theoretische Physik 1, TU Dortmund, Germany

We use linked-cluster expansions to analyze the quantum phase transitions between symmetry-unbroken trivial and topological Haldane phases in two different spin-one chains. The first model is the spin-one Heisenberg chain in the presence of a single-ion anisotropy, while the second one is the dimerized spin-one Heisenberg chain. For both models, we determine the ground-state energy and the one-particle gap inside the nontopological phase as a high-order series using perturbative continuous unitary transformations. Extrapolations of the gap series are applied to locate the quantum critical point and to extract the associated critical exponent. We find that this approach works unsatisfactorily for the anisotropic chain, since the quality of the extrapolation appears insufficient due to the large correlation length exponent. In contrast, extrapolation schemes display very good convergence for the gap closing in the case of the dimerized spin-one Heisenberg chain.