Phase-Controlled Majorana Zero Modes in Altermagnetic Topological-Insulator Josephson Junctions

RESUMO

We exploit facet-dependent Andreev phase shifts to control topological superconductivity with a phase bias in a three-dimensional altermagnetic topological-insulator Josephson junction. In the weak link between two conventional $s$-wave superconductors, the $d$-wave altermagnetic order produces anisotropic momentum shifts of the surface Dirac cones. The resulting net momentum of the states involved in Andreev reflection generates additional propagation phases that differ between facets. Consequently, the facet-resolved Andreev spectra exhibit gap closings at distinct phase biases, giving rise to topological superconducting regimes that host Majorana zero modes (MZMs). We further show that the spatial locations of the MZMs can be controlled by the phase bias. Moreover, these topological superconducting transitions are only weakly affected by moderate variations in the chemical potential, obviating the need for fine-tuning to the Dirac point. Our results establish a platform for realizing and spatially controlling MZMs by tuning the superconducting phase bias in altermagnetic topological-insulator Josephson junctions.