Mathias Scheurer
In the first part of this talk, we discuss how the strategic placement of impurities on an unconventional superconductor, with competing subleading superconducting instabilities, can be used to engineer interesting symmetry-breaking patterns [1]. Using a square-lattice d-wave superconductor as an example, we show that this leads to spontaneous orbital altermagnetic order. This exotic form of order is characterized by a non-trivial arrangement of spontaneous loop currents in the superlattice unit cell that breaks both time-reversal and C4z rotational symmetry but preserves their product. Upon including spin-orbit coupling, altermagnetic correlations are induced in the spin channel as well. In the second part of the talk, we will analyze under which conditions a superconducting diode effect without net magnetization – something that is prohibited in antiferromagnets – is guaranteed to emerge, study its interplay with finite-momentum pairing, and reveal non-trivial magnetic symmetry signatures in the directional dependence of the critical current [2].
[1] Pupim & Scheurer, PRL 134, 146001 (2025) [arXiv:2411.02489]
[2] Banerjee & Scheurer, PRB 110, 024503 (2024) [arXiv:2402.14071]