Searches for Vector-like Quarks, $t\bar{t}$ and $tb$ resonances with the ATLAS Detector

Various extensions of the Standard Model predict the existence of new types of quarks. We report on several search channels such as vector-like quarks decaying to a $Z$ boson and a top quark or bottom quark. We also report results from searches for new resonances decaying to a top-antitop pair and a top-antibottom pair, including the use of boosted top quark reconstruction techniques. These searches use the data sample recorded in 2012 at $\sqrt{s}$=8 TeV centre-of-mass energy by the ATLAS experiment at the LHC. In these searches no evidence for new physics is observed.