Single-valley state in a two-dimensional antiferromagnetic lattice

We propose the concept of single-valley state in two-dimensional antiferromagnetic lattice, which intrinsically holds only one valley and thus robust valley-polarized physics. Using tight-binding model analysis, the physical mechanism to form the single-valley state is illustrated, and large magnetic moment and strong spin-orbit coupling are unveiled to define it. Furthermore, based on first-principles calculations, the single-valley state is predicted in a real material of single-layer $\mathrm{BiFe}{\mathrm{O}}_{3}$. The spontaneous valley polarization in single-layer $\mathrm{BiFe}{\mathrm{O}}_{3}$ is particularly huge, at least one order of magnitude higher than those of all the existing ferrovalley systems. Our work enriches the physics of two-dimensional valleytronics and provides a promising avenue to observe strong valley-polarized phenomena.