Topological properties of finite-size heterostructures of magnetic topological insulators and superconductors

Heterostructures of magnetic topological insulators (MTIs) and superconductors (SCs) in two-dimensional
(2D) slab and one-dimensional (1D) nanoribbon geometries have been predicted to host, respectively, chiral
Majorana edge states (CMESs) and Majorana bound states (MBSs). We study the topological properties of such
MTI/SC heterostructures upon variation of the geometry from wide slabs to quasi-1D nanoribbon systems and
as a function of the chemical potential, the magnetic doping, and the induced superconducting pairing potential.
To do so, we construct effective symmetry-constrained low-energy Hamiltonians accounting for the real-space
confinement. For a nanoribbon geometry with finite width and length, we observe different phases characterized
by CMESs, MBSs, as well as coexisting CMESs and MBSs, as the chemical potential, the magnetic doping,
and/or the width are varied.