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How quantum fluctuations freeze a classical liquid and then melt it into a topological one

  • Hao Chen
  • , Dan Mao
  • , Andrea Kouta Dagnino
  • , Glenn Wagner
  • , Mark H. Fischer
  • , Juraj Hasik
  • , Eun Ah Kim
  • , Titus Neupert

Research output: Contribution to journalArticlepeer-review

Abstract

Topologically ordered quantum liquids are highly sought-after quantum phases of matter, and recently, fractional Chern insulators (FCIs) joined the few experimental realizations of such phases. Here, we ask whether a gapped classical, highly degenerate liquid can be the birthplace of FCIs upon the addition of suitable quantum fluctuations. Two competing tendencies can be anticipated: (1) Following the quantum order-by-disorder paradigm, quantum fluctuations could induce symmetry-breaking (charge) order, or (2) the classical liquid builds up long-range entanglement and turns into a quantum liquid. We study spinless fermions on a honeycomb lattice subject to cluster-charging interactions and introduce quantumness through a Haldane kinetic term, featuring complex second-nearest-neighbor hopping. Based on extensive exact diagonalization calculations and high-order perturbation theory, we find that neither scenario (1) nor (2) prevails, but (1) and (2) manifest sequentially as the kinetic energy is increased. We demonstrate how the gradual lifting of kinematic constraints gives rise to this sequence of phases. Our results relate to the regime of intermediate-scale interactions present in moiré systems, where band projections are not suitable to model FCIs and competing charge-ordered phases have been identified.

Original languageEnglish
Article numberL042021
JournalPhysical Review Research
Volume7
Issue number4
DOIs
StatePublished - Oct 2025

Bibliographical note

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© 2025 authors.

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