Role of Majorana Fermions in high-harmonic generation from Kitaev chain

TL;DR

This paper demonstrates that high-harmonic spectroscopy can detect topological phase transitions in a Kitaev chain by observing the behavior of Majorana edge modes, providing a new tool for studying Majorana fermions in condensed matter.

Contribution

It shows that high-harmonic spectroscopy is sensitive to Majorana edge modes and topological phase transitions in the Kitaev chain with open boundaries, unlike in periodic systems.

Findings

High-harmonic spectra differ between topological and trivial phases with open boundaries.

Edge modes influence the harmonic generation, enabling phase transition detection.

Periodic boundary conditions do not show sensitivity to the phase transition in harmonic spectra.

Abstract

The observation of Majorana fermions as collective excitations in condensed-matter systems is an ongoing quest, and several state-of-the-art experiments have been performed in the last decade. As a potential avenue in this direction, we simulate the high-harmonic spectrum of Kitaev's superconducting chain model that hosts Majorana edge modes in its topological phase. It is well-known that this system exhibits a topological--trivial superconducting phase transition. We demonstrate that high-harmonic spectroscopy is sensitive to the phase transition in presence of open boundary conditions due to the presence or absence of these edge modes. The population dynamics of the Majorana edge modes are different from the bulk modes, which is the underlying reason for the distinct harmonic profile of both the phases. On the contrary, in presence of periodic boundary conditions with only bulk modes, high-harmonic spectroscopy becomes insensitive to the phase transition with similar harmonic profiles in both phases.