  We present high resolution ($0.11"\times0.06"$) 3mm ALMA observations of the
highly inclined transition disk around the star T Cha. Our continuum image
reveals multiple dust structures: an inner disk, a spatially resolved dust gap,
and an outer ring. When fitting sky-brightness models to the real component of
the 3mm visibilities, we infer that the inner emission is compact ($\le1$au in
radius), the gap width is between 18-28 au, and the emission from the outer
ring peaks at $\sim36$ au. We compare our ALMA image with previously published
1.6$\mu$m VLT/SPHERE imagery. This comparison reveals that the location of the
outer ring is wavelength dependent. More specifically, the peak emission of the
3mm ring is at a larger radial distance than that of the 1.6$\mu$m ring,
suggesting that millimeter-sized grains in the outer disk are located further
away from the central star than micron-sized grains. We discuss different
scenarios to explain our findings, including dead zones, star-driven
photoevaporation, and planet-disk interactions. We find that the most likely
origin of the dust gap is from an embedded planet, and estimate --- for a
single planet scenario --- that T Cha's gap is carved by a $1.2M_{jup}$ planet.
