In recent years, high harmonic generation (HHG) from topological matter has attracted considerable interest, emerging as a promising tool for detecting the topological phase. This work incorporates dephasing effects in the theoretical simulations of HHG from topological insulators described by finite-size tight-binding models. This is done by formulating a density-matrix approach in both length and velocity gauges within dipole approximation, with a gauge-invariant treatment of dephasing properly introduced such that the HHG response of a sufficiently large solidlike system is consistent with the periodic limit obtained using semiconductor Bloch equations. Applying the approach to Su-Schrieffer-Heeger chains reveals how dephasing affects the impact of topological edge states on the HHG spectra. It is found that dephasing can either weaken or strengthen the spectral contrast between the topological and trivial phases, depending on which of the intra- and interband mechanisms is dominant for a specific harmonic in the trivial phase.

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• High-order harmonic generation
• Tight-binding model