Conductivity of edge states in 1T-TaS2*

The layered compound TaS2 has been shown to form a commensurate Charge-Density Wave (CCDW) lattice at low temperatures, and undergoes multiple fascinating transitions between nearly-commensurate and incommensurate CDW phases with increasing temperature.  Such phases exhibit unique conductive properties that offer a new platform for next-generation electronic devices, namely the ultra-fast insulator-metal transition observed in CCDW 1T-TaS2 under optical or electric excitation.

Prior work in our group has shown, using a cross-bar device, that one can toggle the resistivity of CCDW-phase TaS2 via directional write currents.  While initially thought to be a slidetronic effect driven by the interlayer alignment of CCDWs, state-of-the-art SQUID measurements of spatially-resolved current density show the current path to orient along lateral edges of the device.  Using first principles calculations, we model the lateral edge states of 1T-TaS2 using a tight-binding approach and demonstrate the formation of mid-gap states that mediate the flow of current along the boundary.  This investigation explores the topological properties of the boundary states, and surveys their sensitivity to stacking and atomic termination.