Semiconducting triferroic multiferroics in van der Waals bilayer lattice

Despite great fundamental and technological importance, triferroic multiferroics are still substantially unexplored, especially their semiconducting characteristics. Here, we propose a design principle for achieving semiconducting triferroic multiferroicity in a bilayer lattice by utilizing van der Waals stacking as a perturbation. We further demonstrate this principle in a real material: bilayer T '-TiBr2. Based on first-principles calculations, we show that bilayer T '-TiBr2 exhibits semiconducting and antiferromagnetic properties. Additionally, its crystal symmetry gives rise to 120 degrees ferroelasticity, and interlayer charge redistribution leads to an out-of-plane electric polarization, thereby realizing the intriguing semiconducting triferroicity. Furthermore, this system is predicted to possess several extraordinary properties, including ferroelastic control of the magnetization orientation and ferroelectric control of the absolute values of spin-polarization-density distributions.