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

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.

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Publication Details

Journal
Physical Review Research
Published
2025-09-25
DOI
https://doi.org/10.1103/ydxb-1tfx
Primary Topic
Topological Materials and Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

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

Glenn Wagner, Juraj Hašík, Mark H. Fischer, Titus Neupert et al.
Physical Review Research
Topological Materials and Phenomena
article

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

Glenn Wagner, Juraj Hašík, Mark H. Fischer, Titus Neupert, Dan Mao, Eun-Ah Kim, Andrea Kouta Dagnino, Hao Chen
article en

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.

Physical Review ResearchVol. 7(4)
Ewha Womans University (KR), University of Zurich (CH), Cornell University (US), ETH Zurich (CH), Ewha Womans University Medical Center (KR)
National Science Foundation, Gordon and Betty Moore Foundation, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Openalex Percentile: Top 75%
Topological Materials and Phenomena
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