%0 Journal Article %T Far-Infrared Excitations below the Kohn Mode: Internal Motion in a Quantum Dot %A Roman Krahne %A Vidar Gudmundsson %A Christian Heyn %A Detlef Heitmann %J Physics %D 2001 %I arXiv %R 10.1103/PhysRevB.63.195303 %X We have investigated the far-infrared response of quantum dots in modulation doped GaAs heterostructures. We observe novel modes at frequencies below the center-of-mass Kohn mode. Comparison with Hartree-RPA calculations show that these modes arise from the flattened potential in our field-effect confined quantum dots. They reflect pronounced relative motion of the charge density with respect to the center-of-mass. %U http://arxiv.org/abs/cond-mat/0102005v1