Strain-Tuned Altermagnetism in a Two-Dimensional Pentagonal Monolayer

Altermagnetism, a newly discovered class of magnetic order, has recently attracted significant research interest [1,2]. This magnetic phase combines properties of two distinct magnetic states: ferromagnetism and antiferromagnetism. In altermagnets, electronic states with opposite spins exhibit energy splitting, reflecting the breaking of time-reversal symmetry, similar to ferromagnetism. However, like antiferromagnets, altermagnets exhibit zero net magnetization. In this study, we report a novel two-dimensional system that exhibits g-wave altermagnetism and undergoes a strain-induced transition from g-wave to d-wave altermagnetism. This system can be realized in an unconventional monolayer pentagonal lattice, and we present a realistic tight-binding model of it incorporating both magnetic and non-magnetic sites. Additionally, we find that non-trivial band topology can emerge in this system by breaking the symmetry protecting the spin-polarized nodal points. Finally, we demonstrate that this g-wave altermagnetism and its expected strain-induced transition can be realized in several candidate materials, such as FeS₂ and Nb₂FeB₂, which exhibit symmetry consistent with the proposed tight-binding Hamiltonian, as shown by first-principles calculations. Our findings will open a new avenue for future exploration of spintronics devices based on altermagnetic systems.

[1] Šmejkal, L., Sinova, J. and Jungwirth, T., 2022. Beyond conventional ferromagnetism and antiferromagnetism: A phase with nonrelativistic spin and crystal rotation symmetry. Physical Review X, 12(3), p.031042.

[2] Šmejkal, L., Sinova, J. and Jungwirth, T., 2022. Emerging research landscape of altermagnetism. Physical Review X, 12(4), p.040501.