Quantum 2025 – wissenschaftliches Programm
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FRI: Friday Contributed Sessions
FRI 11: Quantum 2D-Moiré and Rhombohedral van-der-Waals Systems: Contributed Session to Symposium
FRI 11.6: Vortrag
Freitag, 12. September 2025, 12:00–12:15, ZHG104
Persistent Haldane Phase in Carbon Tetris Chains — •Anas Abdelwahab1, Christoph Karrasch2, and Roman Rausch2 — 1Leibniz Univesität Hannover, Institut für Theoretische Physik, Hannover — 2Technische Universität Braunschweig
We introduce the concept of "tetris chains", which are linear arrays of 4-site molecules that differ by their intermolecular hopping geometry. We investigate the fermionic symmetry-protected topological Haldane phase in these systems using Hubbard-type models. The topological phase diagrams can be understood via different competing limits and mechanisms: strong-coupling U≫ t, weak-coupling U≪ t, and the weak intermolecular hopping limit t′≪ t. Our particular focus is on two tetris chains that are of experimental relevance. First, we show that a "Y-chain" of coarse-grained nanographene molecules (triangulenes) is robustly in the Haldane phase in the whole t′−U plane due to the cooperative nature of the three limits. Secondly, we study a near-homogeneous "Y′-chain" that is closely related to the electronic model for poly(p-phenylene vinylene). In the latter case, the above mechanisms compete, but the Haldane phase manifests robustly and is stable when long-ranged Pariser-Parr-Popple interactions are added. The site-edged Hubbard ladder can also be viewed as a tetris chain, which gives a very general perspective on the emergence of its fermionic Haldane phase. Our numerical results are obtained using the density-matrix-renormalization group as well as the variational uniform matrix-product state (VUMPS) algorithms.
Keywords: symmetry-protected topological statea; quasi one-dimensional spin chains; Density matrix renormalization group