TY  - JOUR
PB  - SciPost Foundation
DO  - 10.21468/SciPostPhys.18.6.178
TI  - Quantum transport theory for unconventional magnets: Interplay of altermagnetism and p-wave magnetism with superconductivity
PY  - 2025/06/05
UR  - https://scipost.org/SciPostPhys.18.6.178
JF  - SciPost Physics
JA  - SciPost Phys.
VL  - 18
IS  - 6
SP  - 178
A1  - Kokkeler, Tim
AU  - Tokatly, Ilya
AU  - Bergeret, F. Sebastian
AB  - We present a quantum transport theory for generic magnetic metals, in which magnetism occurs predominantly due to exchange interactions, such as ferromagnets, antiferromagnets, altermagnets and p-wave magnets. Our theory is valid both for the normal and the superconducting state and is based on the generalization of nonlinear sigma model to such systems. We derive the effective low-energy action for each of these materials, where the symmetries of the corresponding spin space group are used to determine the form of the tensor coefficients appearing in the action. The transport equations, which are obtained as the saddle point equations of this action, describe a wider range of phenomena than the usual quasiclassical equations. In ferromagnets, in addition to the usual exchange field and spin relaxation effects, we identify a spin-dependent renormalization of the diffusion coefficient, and a correction to the Hanle effect. The former provides a description of spin-polarized currents in both the normal and superconducting equal spin-triplet states. In the normal state, our equations provide a complete description of the spin-splitting effect in diffusive systems, recently predicted in ideal clean altermagnets. In the superconducting state, our equations predict a proximity induced magnetization, the appearance of a spontaneous magnetic moment in hybrid superconductor-altermagnet systems. The distribution and polarization direction of this magnetic moment depend on the symmetry of the structure, thus measurements of such polarization reveal the underlying microscopic symmetry of the altermagnet. Finally, for inversion-symmetry-broken antiferromagnets, such as the p-wave magnet, we show that spin-galvanic effects may emerge. This effect is indistinguishable from the spin-galvanic effect induced by spin-orbit coupling in the normal state, but they can be distinguished through the temperature dependence in the superconducting state. Besides these examples, our model applies to arbitrary magnetic systems, providing a complete theory for nonequilibrium transport in diffusive nonconventional magnets at arbitrary temperatures.
ER  -

@Article{10.21468/SciPostPhys.18.6.178,
	title={{Quantum transport theory for unconventional magnets: Interplay of altermagnetism and p-wave magnetism with superconductivity}},
	author={Tim Kokkeler and Ilya Tokatly and F. Sebastian Bergeret},
	journal={SciPost Phys.},
	volume={18},
	pages={178},
	year={2025},
	publisher={SciPost},
	doi={10.21468/SciPostPhys.18.6.178},
	url={https://scipost.org/10.21468/SciPostPhys.18.6.178},
}