Majorana corner modes and tunable braiding in an altermagnet-superconductor heterostructure

Zeeman fields are usually required for realizing and manipulating Majorana corner modes at the cost of suppressed superconducting pairing. Altermagnetism offers a new route toward realizing Majorana corner modes under zero net external magnetic fields. Here we propose a theoretical scheme to host Majorana corner modes in a honeycomb-lattice altermagnet-superconductor heterostructure. In contrast to previous studies on square lattices, altermagnetism yields distinct effective low-energy edge masses on various inequivalent edges of the honeycomb lattice. Within a low-energy edge-theory framework, we establish the conditions under which Majorana corner modes emerge for both bearded and zigzag edge terminations. We further explicitly construct a complete set of Clifford gates by tuning the altermagnetic anisotropy and chemical potential of the heterostructure. Our results provide a promising platform for the realization and manipulation of Majorana corner modes.