Piezovalley and piezoelectric altermagnetism in a 2D Ti₂ClIO semiconductor

Altermagnetic materials with high-performance multipiezo effect have attracted tremendous attention for their potential applications in information storage and logic operations. Here, we propose an altermagnetic monolayer Ti₂ClIO with excellent dynamic, thermal, and mechanical stabilities. The monolayer Ti₂ClIO presents zero net magnetization with an easyxy-plane. Moreover, it is a semiconductor with a direct band gap of 792 meV. The band structure shows a pronounced spin splitting of 914/811 meV for the valence/conduction band. Interestingly, a reversible valley polarization as high as 293 meV is induced in monolayer Ti₂ClIO by applying a uniaxial strain, resulting in the piezovalley effect. Moreover, an out-of-plane piezoelectricity emerges in the present monolayer Ti₂ClIO due to the broken horizontal mirror symmetry, showing the piezoelectric behavior with a strain coefficient of -0.03 pm V^-1. This study unveils a promising candidate for developing multifunctional electronic devices.