Hidden chiral symmetries in BDI multichannel Kitaev chains

TL;DR

This paper reveals hidden BDI symmetries in multichannel Kitaev chains with internal degrees of freedom, enabling the prediction of Majorana states and analyzing symmetry-breaking effects.

Contribution

It generalizes the concept of hidden chiral symmetries to systems with multiple internal degrees of freedom, including spinful 2-band Kitaev chains.

Findings

A Hamiltonian with arbitrary internal degrees of freedom exhibits hidden BDI symmetry.

A 2-band spinful Kitaev chain can host up to 4 Majorana bound states.

Breaking chiral symmetry leads to minigap states.

Abstract

Realistic implementations of the Kitaev chain require, in general, the introduction of extra internal degrees of freedom. In the present work, we discuss the presence of hidden BDI symmetries for free Hamiltonians describing systems with an arbitrary number of internal degrees of freedom. We generalize results of a spinfull Kitaev chain to construct a Hamiltonian with $n$ internal degrees of freedom and obtain the corresponding hidden chiral symmetry. As an explicit application of this generalized result, we exploit by analytical and numerical calculations the case of a spinful 2-band Kitaev chain, which can host up to 4 Majorana bound states. We also observe the appearence of minigap states, when chiral symmetry is broken.