Engineering harmonic emission through spatial modulation in a Kitaev chain

TL;DR

This paper explores how spatial modulation in a Kitaev chain influences high-harmonic generation, revealing controllable emission spectra linked to the system's topological phase and mid-gap states.

Contribution

It introduces a method to control HHG in a topological superconductor via site-dependent modulation, connecting harmonic spectra with topological and mid-gap state properties.

Findings

Different spectral segments correspond to distinct transition mechanisms.

Mid-gap states hybridize with bulk states, affecting harmonic emission.

Harmonic profiles can be tuned by the modulation parameter .

Abstract

We investigate High-harmonic generation (HHG) in a dimerized Kitaev chain. The dimerization in the model is introduced through a site-dependent modulating potential, determined by a parameter $\lambda \in [-1:1]$. This parameter also determines the strength of the hopping amplitudes and tunes the system's topology. Depending upon the parameter $\lambda$, the HHG emission spectrum can be classified into three segments. The first segment exhibits two plateau structures, with the dominant one resulting from transitions to the chiral partner state, consistent with quasiparticle behavior in the topological superconducting phase. The second segment displays multiple plateaus, where intermediate states enable various transition pathways to higher conduction bands. Finally, the third segment presents broader plateaus, indicative of active interband transitions. In the $\lambda\leq0$ regime, we observe the mid-gap states (MGSs) hybridize with the bulk, suppressing the earlier observed harmonic enhancements. This highlights the key role of the intermediate states, particularly when MGSs are isolated. These results demonstrate that harmonic emission profiles can be selectively controlled through the modulating parameter $\lambda$, offering new prospects for tailoring HHG in topological systems.