Enhanced Majorana bound states in magnetic chains on superconducting topological insulator edges

The most promising mechanisms for the formation of Majorana bound states (MBSs) in condensed matter systems involve 1D systems (magnetic chains, nanowires, quantum spin-Hall (QSHI) edge states) proximitized to superconducting materials. In this contribution, we propose that a magnetic chain deposited on a QSHI edge in contact with a superconducting surface, offers a better choice of tunability and MBS robustness compared to the same magnetic chain deposited on the QSHI bulk or a superconduting surface. We show that MBSs near the QSHI edge can be realized with lower chemical potential and Zeeman field than the ones inside the bulk, independently of the chain's magnetic order. Moreover, we quantify the "quality" of MBSs by calculating the Majorana Polarization (MP) for different configurations. For chains located at the edge, the MP is close to its maximum value already for short chains. For chains located away from the edge, longer chains are needed to attain the same quality as chains located at the edge.