Manipulating anomalous transport via crystal symmetry in two-dimensional altermagnets

Anomalous transports, including the anomalous Hall effect (AHE) and anomalous Nernst effect (ANE), are typical manifestations of time-reversal-symmetry-breaking responses in materials. In general, the two Hall states with opposite Hall conductivities can be regarded as time-reversal pairs coupled to magnetic order, and switching between them relies on reversing the magnetization via an external magnetic field or electric current. Here, we introduce an approach for manipulating anomalous transport through crystal symmetry engineering in two-dimensional (2D) altermagnetic systems. Through symmetry analysis and lattice models, we show that for systems with out-of-plane Néel vectors, breaking the symmetry that connects two magnetic sublattices will induce an anomalous Hall response. Crucially, the signs of the anomalous Hall and anomalous Nernst conductivities can be flexibly controlled via symmetry-breaking perturbations, enabling the realizing tunable sign-reversible anomalous transport. Using first-principles calculations, we investigate crystal-symmetry-controlled anomalous transport in the 2D altermagnetic materials V$_{2}$STeO and Cr$_{2}$O$_{2}$. The results indicate that these systems with out-of-plane Néel vectors exhibit pronounced AHE and ANE signals under uniaxial strain. Remarkably, the sign of the anomalous transport coefficients can be reversed by simply rotating the strain direction by $π/2$, thus enabling the switching of anomalous transverse currents without an external magnetic field. Our findings provide a new strategy to manipulate anomalous transport, and should have significant potential applications.