Nanoscale studies of electric field effects on monolayer 1T′-WTe2

Monolayer 1 T '-WTe2 is a quantum spin Hall insulator with a gapped 2D-bulk and gapless helical edge states persisting to temperatures similar to 100 K. Despite the far-ranging interest, the magnitude of the bulk gap, the effect of gating on the 2D-band structure, as well the role interactions are not established. In this work we use STM spectroscopy to measure the intrinsic bulk gap of monolayer 1 T '-WTe2 and show that gate induced electric fields cause large changes of the gap magnitude. Our first-principles DFT-derived tight-binding model reveal that a combination of spatial localization of the conduction and valance bands and Rashba-like spin-orbit coupling leads to a gating induced spin-splitting of the 2D-bulk bands in the tens of meV, thereby reducing the band gap. Our work explains the large sensitivity of the band structure to electric fields and suggests a new avenue for realizing proximity induced non-trivial superconductivity in monolayer 1 T '-WTe2.

Automated summary

In this study, we used STM spectroscopy to measure the intrinsic bulk gap of monolayer 1 T '-WTe2 and demonstrated the significant changes in the gap magnitude induced by gate-induced electric fields. Our first-principles DFT-derived tight-binding model revealed the mechanism of spatial localization of bands and gate-induced spin splitting, providing a new avenue for realizing proximity induced non-trivial superconductivity in monolayer 1 T '-WTe2.