We report scanning tunneling microscopy (STM) and spectroscopy (STS) measurements of monolayer and bilayer WSe2. We measure a band gap of 2.21 ± 0.08 eV in monolayer WSe2, which is much larger than the energy of the photoluminescence peak indicating a large excitonic binding energy. We additionally observe significant electronic scattering arising from atomic-scale defects. Using Fourier transform STS (FT-STS), we map the energy versus momentum dispersion relations for monolayer and bilayer WSe2. Further, by tracking allowed and forbidden scattering channels as a function of energy we infer the spin texture of both the conduction and valence bands. We observe a large spin-splitting of the valence band due to strong spin-orbit coupling, and additionally observe spin-valley-layer coupling in the conduction band of bilayer WSe2.
@article{arxiv.1505.00245,
title = {Local Spectroscopic Characterization of Spin and Layer Polarization in WSe$_2$},
author = {Matthew Yankowitz and Devin McKenzie and Brian J. LeRoy},
journal= {arXiv preprint arXiv:1505.00245},
year = {2015}
}