Detection of charge states of an InAs nanowire triple quantum dot with an integrated nanowire charge sensor

TL;DR

This paper demonstrates an integrated InAs nanowire triple quantum dot with a charge sensor, enabling precise detection of charge states and transitions, even when direct transport signals are weak or indiscernible.

Contribution

The study introduces a novel integrated nanowire charge sensor for a triple quantum dot, improving charge state detection sensitivity and enabling exploration of complex resonance regimes.

Findings

Charge stability diagrams match between transport and charge sensing methods.

The nanowire charge sensor detects charge transitions with high sensitivity.

Regimes with co-existing triple and quadruple points are accessible using the sensor.

Abstract

A linear triple quantum dot (TQD) integrated with a quantum dot (QD) charge sensor is realized. The TQD and the charge sensor are built from two adjacent InAs nanowires by fine finger gate technique. The charge state configurations of the nanowire TQD are studied by measurements of the direct transport signals of the TQD and by detection of the charge state transitions in the TQD via the nanowire QD sensor. Excellent agreements in the charge stability diagrams of the TQD obtained by the direct transport measurements and by the charge-state transition detection measurements are achieved. It is shown that the charge stability diagrams are featured by three groups of charge state transition lines of different slopes, corresponding to the changes in the electron occupation numbers of the three individual QDs in the TQD. It is also shown that the integrated nanowire QD sensor is highly sensitive and can detect the charge state transitions in the cases where the direct transport signals of the TQD are too weak to be measurable. Tuning to a regime, where all the three QDs in the TQD are close to be on resonance with the Fermi level of the source and drain reservoirs and co-existence of triple and quadruple points becomes possible, has also been demonstrated with the help of the charge sensor in the region where the direct transport signals of the TQD are hardly visible.