Signatures of spin pairing in chaotic quantum dots

Coulomb blockade resonances are measured in a GaAs quantum dot in which bot h shape deformations and interactions are small. The parametric evolution o f the Coulomb blockade peaks shows a pronounced pair correlation in both po sition and amplitude, which is interpreted as spin pairing. As a consequenc e, the nearest-neighbor distribution of peak spacings can be well approxima ted by a modified bimodal Wigner surmise, in which interactions are taken i nto account beyond the constant interaction model.