Nonrelativistic and Relativistic Contributions to Spin-Momentum Locking and Spin Photogalvanic Effect in an Altermagnetic Multiferroic
Abstract
Altermagnetic multiferroics provide a platform where non-relativistic spin-momentum locking (SML) coexists with relativistic spin textures, yet disentangling their different origins remains challenging. Here, using first-principles density-functional-theory calculations and symmetry analysis of the multipolar expansion of the spin polarization, we investigate the altermagnetic multiferroic BaCuF4. Its dominant non-relativistic altermagnetic d-wave SML originates primarily from a CuF6 octahedral rotation coupled to the polar distortion and can therefore be reversed by ferroelectric switching. We show that spin-orbit coupling generates additional spin multipoles and, depending on the Neel-vector orientation, induces spin canting and weak ferromagnetism. By exploiting the group-subgroup relations between spin groups and magnetic space groups, we then distinguish non-relativistic altermagnetic, canting-associated, and purely relativistic contributions to the SML. We further show that this hierarchy is encoded in the nonlinear spin-photogalvanic response, whose spin projection selectively probes contributions of different origins. These results establish a direct connection between the microscopic spin texture and nonlinear spin transport in altermagnetic multiferroics.
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BibTeX
@misc{cuono2026nonrelativistic,
title = {{Nonrelativistic and Relativistic Contributions to Spin-Momentum Locking and Spin Photogalvanic Effect in an Altermagnetic Multiferroic}},
author = {Giuseppe Cuono and Subhadeep Bandyopadhyay and Amar Fakhredine and Mathews Benny and Xujia Gong and Paolo Barone and Andrea Droghetti and Carmine Autieri and Silvia Picozzi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37763},
eprint = {2609.37763},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37763},
}
RIS
TY - UNPB
TI - Nonrelativistic and Relativistic Contributions to Spin-Momentum Locking and Spin Photogalvanic Effect in an Altermagnetic Multiferroic
AU - Giuseppe Cuono
AU - Subhadeep Bandyopadhyay
AU - Amar Fakhredine
AU - Mathews Benny
AU - Xujia Gong
AU - Paolo Barone
AU - Andrea Droghetti
AU - Carmine Autieri
AU - Silvia Picozzi
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37763
UR - https://arxiv.org/abs/2609.37763
AB - Altermagnetic multiferroics provide a platform where non-relativistic spin-momentum locking (SML) coexists with relativistic spin textures, yet disentangling their different origins remains challenging. Here, using first-principles density-functional-theory calculations and symmetry analysis of the multipolar expansion of the spin polarization, we investigate the altermagnetic multiferroic BaCuF4. Its dominant non-relativistic altermagnetic d-wave SML originates primarily from a CuF6 octahedral rotation coupled to the polar distortion and can therefore be reversed by ferroelectric switching. We show that spin-orbit coupling generates additional spin multipoles and, depending on the Neel-vector orientation, induces spin canting and weak ferromagnetism. By exploiting the group-subgroup relations between spin groups and magnetic space groups, we then distinguish non-relativistic altermagnetic, canting-associated, and purely relativistic contributions to the SML. We further show that this hierarchy is encoded in the nonlinear spin-photogalvanic response, whose spin projection selectively probes contributions of different origins. These results establish a direct connection between the microscopic spin texture and nonlinear spin transport in altermagnetic multiferroics.
ER -