Quantum spin liquid states have been intensively studied over the past three decades for spin Hamiltonians on the square lattice with short-range interactions which preserve global spin rotation symmetry. Many new theoretical ideas have been developed on this journey, and I will summarize the current understanding. I will then argue that a particular gapless spin liquid state helps us understand several puzzling features of the cuprate phase diagram.
Host: Yong Baek Kim/Arun Paramekanti