Strain-Induced Antiferromagnetic-to-Altermagnetic Phase Transition and Topology in $(\mathrm{CrO}_2)_1/(\mathrm{TaO}_2)_2$ Superlattice

Abstract: Topological aspects in altermagnets have come into focus recently, and tuning the antiferromagnetic (AFM) state into an altermagnetic phase remains an active frontier. We realize both within a rutile superlattice here in this paper. With first principles calculation, we show that a uniaxial strain of only 0.5$\%$ along the c axis converts the $(\mathrm{CrO}_2)_1/(\mathrm{TaO}_2)_2$ rutile superlattice from a trivial antiferromagnet into an altermagnet with topology accompanied by a weak SOC. The strain opens a spin-dependent band splitting of $\sim 1.1 eV$ and, despite the weak SOC together with in-plane magnetic moment orientation, generates an intrinsic anomalous Hall conductivity of order $10^3 S/cm$, comparable magnitude to that in ferromagnetic Weyl semimetals. Tiny SOC here with in-plane (\text{N\'eel}) orientation gaps out the Weyl nodal rings, giving rise to 16 Weyl points in the superlattice. Thus, we point out a simple route toward strain and field tunable, low-dissipation altermagnetic electronics.