Abstract
The electron wave function experiences a phase modification at coherent transmission through a quantum dot. This transmission phase undergoes a characteristic shift of π when scanning through a Coulomb blockade resonance. Between successive resonances either a transmission phase lapse of π or a phase plateau is theoretically expected to occur depending on the parity of quantum dot states. Despite considerable experimental effort, this transmission phase behaviour has remained elusive for a large quantum dot. Here we report on transmission phase measurements across such a large quantum dot hosting hundreds of electrons. Scanning the transmission phase along 14 successive resonances with an original two-path interferometer, we observe both phase lapses and plateaus. We demonstrate that quantum dot deformation alters the sequence of phase lapses and plateaus via parity modifications of the involved quantum dot states. Our findings set a milestone towards an comprehensive understanding of the transmission phase of quantum dots.
Highlights
The electron wave function experiences a phase modification at coherent transmission through a quantum dot
The transmission phase behaviour in between the resonances in principle depends on the spatial symmetries of the quantum dot (QD) states[8,9]: If the involved orbitals have the same parity, a sudden phase lapse of π appears in the valley between two consecutive resonances
The transmission phase measurement is based on Mach–Zehnder interferometry
Summary
The electron wave function experiences a phase modification at coherent transmission through a quantum dot. This transmission phase undergoes a characteristic shift of π when scanning through a Coulomb blockade resonance. Between successive resonances either a transmission phase lapse of π or a phase plateau is theoretically expected to occur depending on the parity of quantum dot states. As one scans through a Coulomb blockade peak, this transmission phase gradually changes The magnitude of this phase shift strongly depends on the coupling of the QD to the leads in the interferometer branch. We find characteristic features of a parity-dependent transmission phase behaviour and demonstrate that the sequence of phase lapses and plateaus can be modified by QD deformation
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