Is 1T-TaS$_2$ a 40 year old quantum spin liquid?

Abstract

1T-TaS$_2$ is unique among transition metal dichalcogenides in that it is understood to be a correlation driven insulator, where the unpaired electron in a 13 site cluster experiences enough correlation to form a Mott insulator. We argue based on existing data that this well-known material should be considered as a quantum spin liquid, either a fully gapped $Z2$ spin liquid or a Dirac spin liquid. We discuss the exotic states that emerge upon doping and propose further experimental probes.