# Spectroscopy of the local density-of-states in nanowires using integrated quantum dots

Thomas, F. S. and Nilsson, M. and Ciaccia, C. and Jünger, C. and Rossi, F. and Zannier, V. and Sorba, L. and Baumgartner, A. and Schönenberger, C.. (2021) Spectroscopy of the local density-of-states in nanowires using integrated quantum dots. Physical Review B, 104 (11). p. 115415.

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Official URL: https://edoc.unibas.ch/86338/

## Abstract

In quantum dot (QD) electron transport experiments additional features can appear in the differential conductance dI/dV that do not originate from discrete states in the QD, but rather from a modulation of the density-of-states (DOS) in the leads. These features are particularly pronounced when the leads are strongly confined low dimensional systems, such as in a nanowire (NW) where transport is one-dimensional and quasi-zero dimensional lead-states can emerge. In this paper we study such lead-states in InAs NWs. We use a QD integrated directly into the NW during the epitaxial growth as an energetically and spatially well-defined tunnel probe to perform dI=dV spectroscopy of discrete bound states in the left' and right' NW lead segments. By tuning a sidegate in close proximity of one lead segment, we can distinguish transport features related to the modulation in the lead DOS and to excited states in the QD. We implement a non-interacting capacitance model and derive expressions for the slopes of QD and lead resonances that appear in two-dimensional plots of dI/dV as a function of source-drain bias and gate voltage in terms of the different lever arms determined by the capacitive couplings. We discuss how the interplay between the lever arms affect the slopes. We verify our model by numerically calculating the dI/dV using a resonant tunneling model with three non-interacting quantum dots in series. Finally, we used the model to describe the measured dI=dV spectra and extract quantitatively the tunnel couplings of the lead segments. Our results constitute an important step towards a quantitative understanding of normal and superconducting subgap states in hybrid NW devices.
Faculties and Departments: 05 Faculty of Science > Departement Physik > Physik > Experimentalphysik Nanoelektronik (Schönenberger) Schönenberger, Christian and Thomas, Frederick and Nilsson, Malin and Ciaccia, Carlo and Jünger, Christian and Baumgartner, Andreas Article, refereed Research Article American Physical Society 2469-9950 2469-9969 Publication type according to Uni Basel Research Database: Journal article Green Open Access 28 Jan 2022 15:45 28 Jan 2022 15:45

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