Valley polarization and anomalous valley Hall effect in altermagnet Ti₂Se₂S with multipiezo properties

Recently, altermagnets demonstrate numerous unique physical phenomena due to their inherent antiferromagnetic coupling and spontaneous spin splitting, which are anticipated to enable innovative spintronic devices. However, the rare two-dimensional altermagnets have been reported, making it difficult to meet the requirements for high-performance spintronic devices on account of the growth big data. Here, we predict a stable monolayer Ti₂Se₂S with out-of-plane altermagnetic ground state and giant valley splitting. The electronic properties of altermagnet Ti₂Se₂S are highly dependent on the onsite electron correlation. Through symmetry analysis, we find that the valleys of X and Y points are protected by the mirror M_xy symmetry rather than the time-reversal symmetry. Therefore, the multipiezo effect, including piezovalley and piezomagnetism, can be induced by the uniaxial strain. The total valley splitting of monolayer Ti₂Se₂S can be as high as ∼ 500 meV. More interestingly, the direction of valley polarization can be effectively tuned by the uniaxial strain; based on this, we have defined logical 0, +1, and −1 states for data transmission and storage. In addition, we have designed a schematic diagram for observing the anomalous Hall effect in the experiment. Our findings have enriched the candidate materials of two-dimensional altermagnet for the ultra-fast and low power consumption device applications.