  Understanding Mott insulators and charge density waves (CDW) is critical for
both fundamental physics and future device applications. However, the
relationship between these two phenomena remains unclear, particularly in
systems close to two-dimensional (2D) limit. In this study, we utilize scanning
tunneling microscopy/spectroscopy to investigate monolayer 1T-NbSe2 to
elucidate the energy of the Mott upper Hubbard band (UHB), and reveal that the
spin-polarized UHB is spatially distributed away from the dz2 orbital at the
center of the CDW unit. Moreover, the UHB shows a root3 x root3 R30{\deg}
periodicity in addition to the typically observed CDW pattern. Furthermore, a
pattern similar to the CDW order is visible deep in the Mott gap, exhibiting
CDW without contribution of the Mott Hubbard band. Based on these findings in
monolayer 1T-NbSe2, we provide novel insights into the relation between the
correlated and collective electronic structures in monolayer 2D systems.
