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Revisiting the J1−J2 Heisenberg model on a triangular lattice: Quasidegenerate ground states and phase competition

Oleksandra Kovalska*,†, Ester Pagès Fontanella*, Benedikt Schneider, Hong-Hao Tu, and Jan von Delft

  • *These authors contributed equally to this work.
  • †Contact author: o.kovalska@lmu.de
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Phys. Rev. B 114, 225105 – Published 5 October, 2026

DOI: https://doi.org/10.1103/cljk-jcq3

Abstract

It is generally believed that the spin-12 triangular-lattice J1−J2 Heisenberg model hosts a quantum spin liquid in the intermediate regime between the 120∘ and stripe ordered phases. Density matrix renormalization group studies on cylinders have consistently found two nearly degenerate ground states, commonly interpreted as distinct topological sectors. Using state-of-the-art matrix product state simulations on YC6 cylinders, we compare the static and dynamical properties of these two sectors at J2/J1=0.125. Noticeable differences appear already in static correlations; moreover, high-resolution dynamical structure factors reveal qualitatively distinct low-energy excitations. These results suggest that the two ground states cannot be understood as merely topologically distinct sectors of a gapped Z2 spin liquid.

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Phys. Rev. B 114, 225105– Published 5 October, 2026
  • Received 19 March 2026
  • Revised 24 August 2026
  • Accepted 28 August 2026
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