The shift current is a non-linear photocurrent generally associated with the underlying quantum geometry. However, a topological origin for the shift photocurrent in non-centrosymmetric systems has recently been proposed. The corresponding topological classification goes beyond the ten-fold paradigm and is associated with the presence of a reverting Thouless pump (RTP). In this work we examine an antiferromagnetic monolayer within the family of MXenes, Ti4C3. This material is centrosymmetric, however, magnetic ordering violates inversion symmetry. We demonstrate evidence of an RTP in each spin-sector which has been perturbed, destroying quantization of the invariant. Nevertheless, a giant spin-resolved shift current persists. We further investigate the mid-gap edge states and classification of the system as a fragile topological insulator to which trivial bands have been coupled.
@article{arxiv.2502.12943,
title = {Evidence for topological origin of large spin-shift current in antiferromagnetic Ti$_{4}$C$_{3}$},
author = {Ali Sufyan and Hasan M. Abdullah and J. Andreas Larsson and Alexander C. Tyner},
journal= {arXiv preprint arXiv:2502.12943},
year = {2025}
}