  Low Density Points (LDPs, \citet{2019ApJ...874....7D}), obtained by removing
high-density regions of observed galaxies, can trace the Large-Scale Structures
(LSSs) of the universe. In particular, it offers an intriguing opportunity to
detect weak gravitational lensing from low-density regions. In this work, we
investigate tomographic cross-correlation between Planck CMB lensing maps and
LDP-traced LSSs, where LDPs are constructed from the DR8 data release of the
DESI legacy imaging survey, with about $10^6$-$10^7$ galaxies. We find that,
due to the large sky coverage (20,000 deg$^2$) and large redshift depth ($z\leq
1.2$), a significant detection ($10\sigma$--$30\sigma$) of the CMB lensing-LDP
cross-correlation in all six redshift bins can be achieved, with a total
significance of $\sim 53\sigma$ over $ \ell\le1024$. Moreover, the measurements
are in good agreement with a theoretical template constructed from our
numerical simulation in the WMAP 9-year $\Lambda$CDM cosmology. A scaling
factor for the lensing amplitude $A_{\rm lens}$ is constrained to $A_{\rm
lens}=1\pm0.12$ for $z<0.2$, $A_{\rm lens}=1.07\pm0.07$ for $0.2<z<0.4$ and
$A_{\rm lens}=1.07\pm0.05$ for $0.4<z<0.6$, with the r-band absolute magnitude
cut of $-21.5$ for LDP selection. A variety of tests have been performed to
check the detection reliability, against variations in LDP samples and galaxy
magnitude cuts, masks, CMB lensing maps, multipole $\ell$ cuts, sky regions,
and photo-z bias. We also perform a cross-correlation measurement between CMB
lensing and galaxy number density, which is consistent with the CMB lensing-LDP
cross-correlation. This work therefore further convincingly demonstrates that
LDP is a competitive tracer of LSS.
