  Two of the most important parameters in supersymmetry are the masses of the
stop and sbottom, the supersymmetric partners of the third generation quarks. A
stop mass lighter than 1 TeV is favored theoretically; however, "conventional"
searches based on the simplified models have not produced experimental evidence
for a light stop. It is possible that the light stop evades our searches due to
a compressed sparticle mass spectrum. Therefore, the searches are extended to
cover a broader range of signal scenarios with different mass splittings
between the stop, neutralino(s), and chargino(s). The searches are then
interpreted in the context of both simplified models and pMSSM models. Recent
ATLAS results from searches for direct stop (sbottom) pair production are
presented in final states with jets and missing transverse-momentum (and
leptons). The analyses are based on 36 fb$^{-1}$ of $\sqrt{s}$=13 TeV
proton-proton collision data recorded with ATLAS detector at the LHC in 2015
and 2016.
