Speaker
Description
In this talk, I address the fundamental question of how the superconducting state is defined in altermagnetic metals. Although these systems are characterized by spin-split Fermi surfaces and a compensated Néel-type magnetic order, the microscopic nature and symmetry classification of their superconducting instabilities remain incompletely understood.
Employing realistic microscopic models that explicitly resolve the essential altermagnetic sublattice degrees of freedom, I demonstrate that the sublattice structure constitutes a primary controlling factor of the superconducting gap topology. Specifically, for superconducting states stabilized by momentum-independent bare attractive interactions, I find that the underlying symmetry of the altermagnetic lattice rigorously enforces gap nodes at the Brillouin-zone boundaries.
I subsequently contrast these results with the case of superconductivity arising from extended-range interactions. In this regime, I demonstrate that Cooper pairing is allowed on the Brillouin-zone boundaries, which enables the stabilization of both spin-singlet and equal-spin-pairing triplet superconducting states. A principal conclusion of this study is that equal-spin-pairing triplet superconductivity is generically energetically favored when the altermagnetic spin splitting of the electronic bands is large compared to the characteristic superconducting gap scale.
Finally, I will discuss how these triplet states feature characteristic non-unitary properties that arise as a direct consequence of the altermagnetic order. By focusing on the interplay between sublattice degrees of freedom and pairing symmetry, I provide a theoretical framework for identifying these unconventional states in candidate altermagnetic materials.