Topological superconductivity in two-dimensional altermagnetic metals

By D. Zhu, Zhengping Zhuang, Zhigang Wu, Zhongbo Yan. Physical review B, 2023

178 citations recorded by the source corpus.

Bringing magnetic metals into superconducting states represents an important approach for realizing unconventional superconductors and potentially even topological superconductors. Altermagnetism, classified as a third basic collinear magnetic phase, gives rise to intriguing momentum-dependent spin-splitting of the band structure, and results in an even number of spin-polarized Fermi surfaces due to the symmetry-enforced zero net magnetization. In this work, we investigate the effect of this new magnetic order on the superconductivity of a two-dimensional metal with $d$-wave altermagnetism and Rashba spin-orbital coupling. Specifically we determine the types of superconducting pairing that can occur in this system and ascertain whether they possess topological properties. Through self-consistent mean-field calculations, we find that the system in general favors a mixture of spin-singlet $s$-wave and spin-triplet $p$-wave pairings, due to the absence of time-reversal symmetry and inversion symmetry. Using symmetry arguments supported by detailed calculations, we show that a number of topological superconductors, including both first-order and second-order ones, can emerge when the $p$-wave pairing dominates. In particular, we find that the second-order topological superconductor is enforced by a $\mathcal{C}_{4z}\mathcal{T}$ symmetry, which renders the spin polarization of Majorana corner modes into a unique entangled structure. Our study demonstrates that altermagnetic metals are fascinating platforms for the exploration of intrinsic unconventional superconductivity and topological superconductivity.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/f49c7f1318e30608bcab1e4d0e3eea99038a638e