1T-TaS

In solids with an odd number of electrons per unit cell, band theory requires that they are metals, but strong interaction can turn them into insulators, called Mott insulators. In this case, the electrons form local moments that, in turn, form an antiferromagnetic ground state. In 1973, P. W. Anderson proposed that, in certain cases, quantum fluctuations may prevent magnetic order and result in a paramagnetic ground state called a quantum spin liquid. After many years of searching, a few examples have been discovered in the past several years. We point out that a well-studied material, TaS2, may be a spin liquid candidate. We propose further experiments that probe the exotic properties of this new state of matter.