Transport signatures of symmetry protection in 1D Floquet topological insulators

Abstract

Time-periodic external drives have emerged as a powerful tool to artificially create topological phases of matter. Prime examples are Floquet topological insulators (FTIs), where a gapped bulk supports in-gap edge states, protected against symmetry-preserving local perturbations. Similar to an ordinary static topological insulator, the robustness of an edge state in a one-dimensional (1D) FTI shows up as a pinning of its quasienergy level, but now inside one of two distinct bulk gaps. Here we propose a scheme for probing this unique feature by observing transport characteristics of a 1D finite-sized FTI attached to external leads. We present predictions for transmission spectra using a nonequilibrium Green's function approach. Our analysis covers FTIs with time-independent and periodically driven boundary perturbations which either preserve or break the protecting chiral symmetry.

Dynamical relaxation of correlators in periodically driven integrable quantum systems

“…We will now consider driving this system periodically in time [54][55][56][57][58][59] by adding a term to the hopping which is of the form a sin(ωt ), where a and ω are the driving amplitude and frequency, respectively. The Hamiltonian in momentum space is therefore given by…”

Quantum dot coupled to topological insulators: The role of edge states

“…Apart from the original polymer system, the SSH model was realized experimentally and the topological edge states were detected in more controllable settings such as cold atoms [20][21][22][23], electronic states in artificial atomic lattices [24] or superlattices [25], mechanical chains [26], and photonic systems [27][28][29]. Among theoretically predicted signatures of the topological edge states are effects in the entanglement entropy [30], in the decoherence of a coupled qubit [31], and in transport and noise characteristics in non-equilibrium settings where a current is driven through an SSH chain [32][33][34][35][36]. However, to the best of our knowledge, the archetypal mesoscopic setup of a quantum dot coupled to leads has not yet been studied if the latter are modeled as SSH chains.…”

Impurity Screening and Friedel Oscillations in Floquet-driven Two-dimensional Metals

“…Periodically driving a solid by strong irradiation renormalizes its equilibrium band structure nonperturbatively, allowing on-demand control of the properties of the irradiated system through the laser intensity and frequency. This approach has been dubbed Floquet engineering [1,2] and has generated considerable recent interest in the properties of Floquet-driven systems, such as tunneling currents [3][4][5][6][7], indirect magnetic exchange interaction [8,9], transport [10][11][12][13][14][15][16][17][18][19] and optical response [20][21][22]. In addition to the dynamic control of material properties, Floquet-driven systems can exhibit nontrivial topological phases [23][24][25][26].…”

“…Screening effects, for example, play an important role in transport which is limited by the screened impurity potential in a disordered sample. Transport in Floquet-driven systems have been largely studied [10][11][12][13][14][15][16][17] in the ballistic regime where scattering with screened external impurities is absent. In general, consideration of time-dependent screening in non-equilibrium situations is a formidable many-body problem requiring a numerical solution of both the Dyson's equation and the quantum kinetic equation [27].…”