Critical-to-Insulator Transitions and Fractality Edges in Perturbed Flatbands

Abstract

We study the effect of quasiperiodic perturbations on one-dimensional all-bands-flat lattice models. Such networks can be diagonalized by a finite sequence of local unitary transformations parameterized by angles ${\theta }_i$. Without loss of generality, we focus on the case of two bands with bandgap $\Delta$. Weak perturbations lead to an effective Hamiltonian with both on- and off-diagonal quasiperiodic terms that depend on ${\theta }_i$. For some angle values, the effective model coincides with the extended Harper model. By varying the parameters of the quasiperiodic potentials, \iffalse and the manifold angles ${\theta }_i$ \fi we observe localized insulating states and an entire parameter range hosting critical states with subdiffusive transport. For finite quasiperiodic potential strength, the critical-to-insulating transition becomes energy dependent with what we term fractality edges separating localized from critical states.

10 pages, 6 figures, 1 table

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• Quasiperiodicity hinders ergodic Floquet eigenstates
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• Exact non-Hermitian mobility edges and robust flat bands in two-dimensional Lieb lattices with imaginary quasiperiodic potentials
• Multifractality in the interacting disordered Tavis-Cummings model
• Critical States Generators from Perturbed Flatbands
• Robust extended states in Anderson model on partially disordered random regular graphs
• Trapping Hard-Core Bosons in Flatband Lattices
• Interplay of many-body interactions and quasiperiodic disorder in the all-band-flat diamond chain
• Fate of localization features in a one-dimensional non-Hermitian flat-band lattice with quasiperiodic modulations
• Many-body critical phase in a quasiperiodic chain and dynamical Widom lines in Fock space properties
• Structural constraints on mobility edges in one-dimensional quasiperiodic systems
• The Wishart--Rosenzweig--Porter random matrix ensemble
• Ergodicity-breaking phase diagram and fractal dimensions in long-range models with generically correlated disorder
• Replica approach to the generalized Rosenzweig-Porter model