Non-universal transmission phase behaviour of a large quantum dot

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.

Coherent transport through a Majorana island in an Aharonov–Bohm interferometer

“…In addition, interferometry offers a way to distinguish between localized trivial modes and MZMs 12,14 . This technique was used to investigate coherent transport in semiconductor quantum dots [17][18][19][20] .…”

Correlation between peak-height modulation and phase lapses in transport through quantum dots

“…The absence of a phase lapse is related with a non-vanishing of the transmission between two resonances. Recently, such a behavior has been experimentally verified for relatively large quantum dots [31] through the observation of missing phase-lapses correlated with nonnegligible values of the conductance between the adjacent resonances.…”

“…While the early experiments [23,24] showed sequences of perfectly universal phase evolution with phase-lapses in every conductance valley (except for extremely low electron fillings in the dot [25]), recent measurements using a new way to reliably extract the transmission phase from the conductance of an Aharonov-Bohm interferometer [29] detected several conductance minima without phase-lapses [30,31]. Though it has not been possible to achieve a complete statistics in these last experiments, the findings are consistent with the predicted departure from the universal behavior of a perfect phase-locking of conductance peaks [26,28].…”

Phase-Coherent Dynamics of Quantum Devices with Local Interactions

“…This quantization is known to induce Coulomb blockade in the conductance of the device, see Figure 3 . Nevertheless, a Coulomb blockaded dot acts at low energy as an elastic scatterer imprinting a phase [ 81 , 82 ] related to its average occupation via the Friedel sum rule, see Section 3.2 . For weak transmissions, strongly deviates from the classical value .…”