N\'eel vector controlled charge and spin transport in altermagnetic junctions.

Altermagnets (AMs) - magnetic materials that have spin-split bandstructure with zero net spin polarization can be classified as weak or strong depending upon the strength of altermagnetic term in the Hamiltonian. We theoretically investigate electron transport in junctions between the two AMs in strong and weak altermagnetic phases. The charge and spin conductivities are analyzed as functions of angle between the N\'eel vectors of the two AMs. In the strong AM regime, the charge conductivity vanishes as, while in the weak AM regime it remains finite. Introducing a normal metal (NM) between two AMs leads to Fabry-P\'erot-type oscillations in charge conductivity which can be controlled by an applied gate voltage. In the strong regime, transport in AM-NM-AM junctions is dominated by up-spin electrons, whereas both spin channels contribute in the weak regime. These results highlight the potential of AM-based heterostructures for spintronic applications, such as spin filters, and quantum interference-based spintronic devices, where tunable spin-dependent transport and interference effects can be utilized in electronic devices without a need for externally applied magnetic field.