Early Stage Researcher 2, CNRS, FRANCE

 

Project title and work package:

Adjustable magnetism of a quantum dot coupled to a superconductor, work package Electron transport in reduced dimensionality.

 

Objectives:

What is the electronic spectrum and the spatial extent of Andreev bound states in a quantum dot coupled to a superconductor? According to the parity of the quantum dot electronic occupation, it can behave as a magnetic impurity or not, producing a scattering centre for the spatial diffusion of Cooper pairs. You will answer this important and quite generic question using a novel approach. In collaboration for the theory with Early Stage Researchers 3 (CNRS, France) and 7 (UKON, Germany), this study will bring a deeper knowledge of the nature of Andreev localised states that are key for the understanding of mesoscopic superconducting structures.

You will fabricate superconducting substrates (niobium, or rhenium, inert when epitaxial) covered with a network of gate electrodes that are isolated from the substrate. You will make use of an all-metal mask lift-off recipe already available at CNRS, enabling the use of refractory metals like Nb without contamination. Nanoparticles (or molecules) will be deposited on the superconducting substrate. The coupling to the gate will be strong for the nanoparticles deposited close to the gates. The gate electrodes will be used to adjust the occupancy of the electronic nanoparticle, which will tune the local magnetism. By performing scanning tunnelling spectroscopy in the vicinity of particles with a variable coupling to the superconducting plane, you will study the competition of superconductivity and the Kondo effect in real space, with unprecedented energy resolution. You will also collaborate with Early Stage Researcher 10 (CTH, Sweden) on the spectroscopy of graphene nanoribbons.

 

Expected Results:

- Spectroscopy of Andreev bound states in a nanoparticle coupled to a superconductor.

- Understanding of the competition between Kondo effect and superconductivity in a quantum dot.

 

Planned secondments:

at Attocube, Germany (2 months, Year 1) to learn about AFM under extreme conditions, at CTH, Sweden (1 month, Year 2) to get trained on molecular and graphene-based electronics, at ETH, Switzerland (1 month, Year 2) to get trained on Scanning Gate Microscopy and Electric Force Microscopy at very low temperature.

 

RESEARCHER IN CHARGE:

clemens.winkelmann@neel.cnrs.fr

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