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Impurity states in altermagnetic superconductors

Andrea Maiani1 and Rubén Seoane Souto2

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Phys. Rev. B 111, 224506 – Published 12 June, 2025

DOI: https://doi.org/10.1103/f6nc-vsnx

Abstract

Altermagnetic superconductors offer the possibility of exploring unconventional superconductivity, including topological states and finite-momentum superconductivity, with promising applications in spintronics and quantum information. However, a direct experimental confirmation of their existence remains elusive. In this work, we propose nonmagnetic impurities as probes of the interplay between altermagnetism and superconductivity. These impurities induce spin-polarized subgap states whose spatial extension reflects the magnetic order of the substrate material. Depending on whether or not the impurity respects the bulk symmetries, these states form spin-degenerate or spin-split doublets. An external magnetic field aligned with the Néel vector can further control the doublet splitting. We further demonstrate that coupling between impurity states leads to a position-dependent, spin-sensitive hybridization, enabling another approach for in situ control of atomic-size quantum devices. These findings provide unambiguous experimental signatures of altermagnetic superconductivity accessible via local measurements such as scanning tunneling microscopy and open unexplored pathways for designing tunable quantum devices.

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Phys. Rev. B 111, 224506– Published 12 June, 2025
  • Received 16 September 2024
  • Revised 27 February 2025
  • Accepted 28 May 2025
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