Scanning Tunneling Spectroscopy Probing the Origin of Charge Density Waves in NbSe2 Erick F. Andrade1, C.J.Arguello1, E.Rosenthal1, W. Jin1, P. C. Yeh1, N. Zaki1, R. M. Fernandes2, A.J.Millis1, R. M. Osgood1, A. N. Pasupathy1 1 Columbia University, 2University of Minnesota Using scanning tunneling microscopy, we address the relationship between quasiparticle interference, the charge susceptibility and the scattering potential in 2H-NbSe2. We show that the charge susceptibility in a quasi-2D material can be directly obtained from quasiparticle interference images, and with the additional ARPES bandstructure measurements, one can extract the wavevector dependence of the scattering potential. Applying these concepts to lightly sulfurdoped 2H-NbSe2, we show that Fermi surface nesting is inconsequential to the charge density wave formation in this material, and that interband scattering dominates possibly arising from strong electron-phonon coupling. efa2108@columbia.edu