  Stellar bars in disk galaxies grow by losing angular momentum to their
environments, including the Dark Matter (DM) halo, stellar and gas disks, and
interacting satellite galaxies. This exchange of angular momentum during galaxy
evolution hints at a connection between bar properties and the DM halo spin
$\lambda$ -- the dimensionless form of DM angular momentum. We investigate the
connection of halo spin $\lambda$ and galaxy properties in the presence/absence
of stellar bars, using the cosmological magneto-hydrodynamic TNG50 simulations
at three redshifts $z_r=0, 0.1$ and 1. We estimate the halo spin for barred and
unbarred galaxies (bar strength: $0<A_2/A_0<0.7$) at the central regions of the
DM halo close to the galaxy disk and far from the disk, close to halo virial
radius. At $z_r=0$, strongly barred galaxies ($A_2/A_0>0.4$) reside in DM halos
having low spin and low specific angular momentum, while unbarred and weakly
barred galaxies ($A_2/A_0<0.2$) are hosted in high spin and high specific
angular momentum halos. The inverse correlation between bar strength and halo
spin is surprising since previous studies show that bars transfer angular
momentum to DM halos. However, the bar strength-halo spin connection is more
complex at higher redshift ($z_r=1$) with higher halo spin for all galaxies
than that at $z_r=0$. Using galaxy samples across various DM halo mass ranges,
we highlight the importance of sample selection in obtaining meaningful
results. Investigating the bar--halo connection in further detail is crucial
for understanding the impact of bars on galaxy evolution models.
