Flatbands under Correlated Perturbations

Abstract

Flatband networks are characterized by the coexistence of dispersive and flatbands. Flatbands (FBs) are generated by compact localized eigenstates (CLSs) with local network symmetries, based on destructive interference. Correlated disorder and quasiperiodic potentials hybridize CLSs without additional renormalization, yet with surprising consequences: (i) states are expelled from the FB energy ${E}_{\mathrm{FB}}$, (ii) the localization length of eigenstates vanishes as $$\xi${}$\sim${}1/\mathrm{ln}(E$-${}{E}_{\mathrm{FB}})$, (iii) the density of states diverges logarithmically (particle-hole symmetry) and algebraically (no particle-hole symmetry), and (iv) mobility edge curves show algebraic singularities at ${E}_{\mathrm{FB}}$. Our analytical results are based on perturbative expansions of the CLSs and supported by numerical data in one and two lattice dimensions.