Ballistic transport and crystallographic control in altermagnetic quantum rings

Abstract

We study coherent two-terminal transport through a finite-width $d$-wave altermagnetic quantum ring with nonmagnetic leads. A confined Aharonov--Bohm flux remains exactly $h/e$ periodic and, in the symmetric one-mode geometry, produces an exact half-flux transmission zero. A perpendicular field shifts the interference pattern according to an effective area $A_{\mathrm{eff}}=1.0342\pi r_0^2$ and the altermagnetic splitting resolves the common zero into nearby spin-dependent nodes. Rotating the crystal reverses the transmitted spin, whereas the mirror orientation ${\theta }_A=\pi /4$ is exactly spin degenerate. For a $50$~nm reference ring, sub-tesla fields yield windows with $|P_T|>0.99$, the most accessible of which requires a uniform field alone and no confined flux. Finite-bias, thermal, disorder, Zeeman, and spin-conserving voltage-probe calculations show that the polarization is appreciably more stable than individual coherent-resonance amplitudes. These results identify interference-node positions, flux periodicity, and crystal-controlled spin polarization as experimentally useful signatures of an altermagnetic mesoscopic interferometer.

arXiv comment22 pages, 12 figures, 5 tables