Boltzmann-constrained extraction of spin splitting and momentum relaxation in -wave altermagnets
Phys. Rev. B 114, 214402 – Published 2 October, 2026
DOI: https://doi.org/10.1103/mnsj-zcyw
Abstract
Altermagnets exhibit spin-split electronic structure without requiring spin-orbit coupling, but transport measurements generally mix intrinsic spin splitting with extrinsic scattering. We examine this identifiability problem for a two-dimensional -wave altermagnet within a unified semiclassical framework spanning ballistic to diffusive transport. The spin-dependent Fermi-surface anisotropy produces a pronounced size effect, where vastly different longitudinal velocities cause the two spin channels to exhibit markedly different effective relaxation lengths within the same device geometry. However, the altermagnetic coupling and the momentum relaxation time strongly compensate each other in longitudinal conductance, producing strong parameter correlation. To address this inverse problem, we formulate a physics-informed neural network (PINN) as a differentiable Boltzmann solver with contact-injection and current-continuity losses and a particle-conserving local distribution. Driven by sparse synthetic conductance spectra, this solver uses the Fermi-level dependence of transport to recover the coupled parameters under the tested conditions, including joint inversion at 1% Gaussian noise and single-parameter extraction at noise levels up to 10%. These results demonstrate parameter recovery by combining Fermi-level-dependent transport data with a physically constrained numerical solver within the model and parameter range studied.