Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Frustrated Magnets - General 2 (joint session TT/MA)

TT 33.2: Vortrag

Dienstag, 2. April 2019, 14:15–14:30, Theater

Spin-1/2 Heisenberg antiferromagnet on the star lattice: Competing valence-bond-solid phases studied by means of tensor networks — •Saeed Jahromi and Roman Orus — Donostia International Physics Center (DIPC) Paseo Manuel de Lardizabal 4 20018 Donostia - San Sebastian (Guipuzkoa), Spain

Using the infinite projected entangled pair states algorithm, we study the ground-state properties of the spin-1/2 quantum Heisenberg antiferromagnet on the star lattice in the thermodynamic limit. By analyzing the ground-state energy of the two inequivalent bonds of the lattice in different unit-cell structures, we identify two competing valence-bond-solid (VBS) phases for different antiferromagnetic Heisenberg exchange couplings. More precisely, we observe (i) a VBS state which respects the full symmetries of the Hamiltonian, and (ii) a resonating VBS state which, in contrast to previous predictions, has a six-site unit-cell order and breaks C3 symmetry. We also studied the ground-state phase diagram by measuring the ground-state fidelity and energy derivatives, and further confirmed the continuous nature of the quantum phase transition in the system. Moreover, an analysis of the isotropic point shows that its ground state is also a VBS as in (i), which is as well in contrast with previous predictions.