Altermagnetism Induced Bogoliubov Fermi Surfaces Form Topological Superconductivity

TL;DR

This paper introduces a new form of topological superconductivity driven by altermagnetic Bogoliubov Fermi surfaces, enabling the realization of Majorana zero modes through anisotropic gaps and quantum confinement effects.

Contribution

It demonstrates how altermagnetic order combined with superconductivity creates novel BFSs and topological phases, providing new platforms for Majorana zero modes in topological superconductors.

Findings

Identification of BFSs in altermagnetic topological insulators.

Proposal of nanowire structures with topological phase transitions.

Discovery of distinct MZMs at vortex lines and boundaries.

Abstract

We propose a novel type of topological superconductivity based on Bogoliubov Fermi surfaces (BFSs) in an altermagnetic topological insulator proximitized by an s-wave superconductor. The 3D altermagnetic topological insulator is characterized by zero-energy surface states in bulk nodal-ring phases and anisotropically shifted surface Dirac cones in topological insulating phases. It is potentially realized in \mathrm{EuIn_{2}As_{2}}. The altermagnetic order in combination with superconductivity gives rise to highly anisotropic superconducting gaps with crystal-facet-dependent BFSs at the physical boundaries. These particular BFSs provide distinct platforms to realize Majorana zero modes (MZMs). We propose a quasi-1D nanowire in which the anisotropic BFSs experience topological phase transitions due to quantum confinement leading to MZMs at its ends. We further consider vortex phase transitions in the superconducting altermagnetic topological insulators. Remarkably, we find that the altermagnetic order allows us to transit between two distinct type of MZMs, one type is located at the vortex line, while the other type is located at the physical boundaries. Our work paves a new avenue utilizing altermagnetism-induced BFSs to engineer topological superconductivity through crystal anisotropy and quantum confinement.