paper

Periodic and aperiodic dynamics of flat bands in diamond-octagon lattice

arXiv:2001.01378 · doi:10.1103/PhysRevB.104.134307

Abstract

We drive periodically a two-dimensional diamond-octagon lattice model by switching between two Hamiltonian corresponding two different magnetic flux piercing through diamond plaquette to investigate the generation of topological flat bands. We show that in this way, the flatness and topological nature of all the bands of the model can be tuned and Floquet quasi-sates can be made topologically flat while its static counterpart does not support the existence of topology and flatness together. By redefining the flatness accordingly in the context of non-equilibrium dynamics and correctly justifying it using the Floquet joint density of states, one indeed obtains a better control of the desired result when the input parameter space composed of temporal window associated with the step Hamiltonian and flux becomes larger than the static parameter space consisting of magnetic flux only. Interestingly, we find the generation of flux current. We systematically analyse the work done and flux current in the asymptotic limit as a function of input parameters to show that topology and flatness both share a close connection to the flux current and work done, respectively. We finally extend our investigation to the aperiodic array of step Hamiltonian, where we find that the heating up problem can be significantly reduced if the initial state is substantially flat as initial the large degeneracy of states prevents the system from absorbing energy easily from the aperiodic driving. We additionally show that the heating can be reduced if the values of the magnetic flux in the step Hamiltonian are small, the duration of these flux are unequal and on the initial flatness of the band. We successfully explain our finding by plausible analytical arguments.

arXiv comment14 pages and 14 figures

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