In this lecture we will focus on frustrated spin systems in two dimensions. Such systems can host a spin liquid, which is a topologically ordered phase preserving both spin and lattice symmetries. Using simple projected entangled-pair states (PEPS), we will address frustrated antiferromagnetic Heisenberg model on a square lattice. In particular, we will discuss an efficient parametrization of PEPS motivated by spatial symmetries, allowing their fast optimization. Furthermore, by explicitly breaking the time-reversal symmetry
the system will develop a chiral spin liquid phase and we will look at its PEPS description.