Fractionalization on the Surface: Is Type-II Terminated 1T-TaS2 Surface an Anomalously Realized Spin Liquid?

Abstract

The type-II terminated 1T-TaS2 surface of a three-dimensional 1T-TaS2 bulk material realizes the effective spin-1/2 degree of freedom on each David star cluster with T2=-1 such that the time-reversal symmetry is realized anomalously, despite the fact that bulk three-dimensional 1T-TaS2 material has an even number of electrons per unit cell with T2=+1. This surface is effectively viewed as a spin-1/2 triangular lattice magnet, except with a fully gapped topological bulk. We further propose this surface termination realizes a spinon Fermi surface spin liquid with the surface fractionalization but with a nonexotic three-dimensional bulk. We analyze possible experimental consequences, especially the surface spectroscopic measurements, of the type-II terminated surface spin liquid.