Superconducting diode effect from field-induced s+if pairing in Ising superconductors

@misc{levchenko2026superconducting,
  title = {{Superconducting diode effect from field-induced $s+if$ pairing in Ising superconductors}},
  author = {Alex Levchenko and Maxim Khodas},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.01476},
  eprint = {2609.01476},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.01476},
}

TY  - UNPB
TI  - Superconducting diode effect from field-induced s+if pairing in Ising superconductors
AU  - Alex Levchenko
AU  - Maxim Khodas
PY  - 2026
DA  - 2026/09/01
PB  - arXiv
DO  - 10.48550/arxiv.2609.01476
UR  - https://arxiv.org/abs/2609.01476
AB  - The in-plane critical field of Ising superconductors exceeds the Pauli limit by an order of magnitude because the Ising spin-orbit coupling locks the electron spins out of the basal plane. The same locking converts an in-plane Zeeman field into a source of equal-spin triplet Cooper pairs, so that the field-driven condensate acquires an s+if character. We show that this conversion channel also generates Lifshitz invariants, the odd-in-momentum terms of the Ginzburg-Landau expansion responsible for the superconducting diode effect. When the basal mirror symmetry of the monolayer is lifted by a substrate or a gate, the field-induced triplets couple linearly to the Cooper-pair momentum, and an intrinsic diode response develops whose strength is set by the ratio of the Zeeman and spin-orbit energies rather than by the small ratio of the spin-orbit and Fermi energies familiar from parity-mixing mechanisms. We construct the symmetry-constrained two-component Ginzburg-Landau theory of the coupled singlet and triplet order parameters and derive all of its coefficients from the microscopic model of an Ising superconductor; the complete functional, including all gradient and quartic terms, is generated by a single pair-breaking function of temperature, field, and Cooper-pair momentum. An attractive triplet channel reshapes the diode response: at weak fields it suppresses the efficiency through destructive interference between the direct and the collective-mode conversion paths, while at strong fields it extends the diode regime well beyond the singlet-only critical field, with the maximal efficiency reached along the triplet-enhanced phase boundary. The diode effect thereby serves as a transport probe of a hidden triplet pairing channel and of the field-induced s+if state.
ER  -