Fate of chiral order and impurity self-pinning in flat bands with local symmetry
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arXiv
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| Autores principales: | , , , |
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| Formato: | Preprint |
| Publicado: |
2024
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| _version_ | 1866916786230788096 |
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| author | Burgher, Maxime Di Liberto, Marco Goldman, Nathan Amelio, Ivan |
| author_facet | Burgher, Maxime Di Liberto, Marco Goldman, Nathan Amelio, Ivan |
| contents | Interacting bosons on a single plaquette threaded by a $π$-flux can spontaneously break time-reversal symmetry, resulting in a chiral loop current. Connecting such bosonic $π$-flux plaquettes in a dispersive configuration was recently shown to lead to long-range chiral order. Here, instead, we design a chain of $π$-flux plaquettes that exhibits an all-flat-bands single-particle energy spectrum and an extensive set of local symmetries. Using Elitzur's theorem, we show that these local symmetries prevent the emergence of long-range chiral order. Moreover, projecting the dynamics to a Creutz ladder model with an effective intra-rung interaction allows one to derive simple spin Hamiltonians capturing the ground state degeneracy and the low-energy excitations, and to confirm the absence of chiral order. Nevertheless, we show how to obtain gauge-invariant information from a mean-field approach, which explicitly break gauge-invaraince. Finally, we observe an ``impurity self-pinning'' phenomenon, when an extra boson is added on top of a ground state at integer filling, resulting in a non-dispersive density peak. Exact diagonalization benchmarks are also provided, and experimental perspectives are discussed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_01780 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Fate of chiral order and impurity self-pinning in flat bands with local symmetry Burgher, Maxime Di Liberto, Marco Goldman, Nathan Amelio, Ivan Quantum Gases Interacting bosons on a single plaquette threaded by a $π$-flux can spontaneously break time-reversal symmetry, resulting in a chiral loop current. Connecting such bosonic $π$-flux plaquettes in a dispersive configuration was recently shown to lead to long-range chiral order. Here, instead, we design a chain of $π$-flux plaquettes that exhibits an all-flat-bands single-particle energy spectrum and an extensive set of local symmetries. Using Elitzur's theorem, we show that these local symmetries prevent the emergence of long-range chiral order. Moreover, projecting the dynamics to a Creutz ladder model with an effective intra-rung interaction allows one to derive simple spin Hamiltonians capturing the ground state degeneracy and the low-energy excitations, and to confirm the absence of chiral order. Nevertheless, we show how to obtain gauge-invariant information from a mean-field approach, which explicitly break gauge-invaraince. Finally, we observe an ``impurity self-pinning'' phenomenon, when an extra boson is added on top of a ground state at integer filling, resulting in a non-dispersive density peak. Exact diagonalization benchmarks are also provided, and experimental perspectives are discussed. |
| title | Fate of chiral order and impurity self-pinning in flat bands with local symmetry |
| topic | Quantum Gases |
| url | https://arxiv.org/abs/2410.01780 |