We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy √s=1.96TeV. This search was conducted within the framework of the R parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of 1fb⊃-1 collected by the Collider Detector at Fermilab experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence level in the stop quark versus sneutrino mass plane are set. Stop quark masses up to 180GeV/c2 are excluded for sneutrino masses around 45GeV/c2, and sneutrino masses up to 116GeV/c2 are excluded for stop quark masses around 150GeV/c2. © 2010 The American Physical Society.