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Mise en évidence de textures de spin synthétiques par des mesures de transport et de champ microonde

Abstract : In this thesis, we have studied carbon nanotube-based nanocircuits integrated in a microwave cavity architecture. Our device is compatible with the simultaneous measurement of both the current through the nanocircuit and the frequency shift of the cavity. These two signals give complementary information about the device. In the two experiments presented in this thesis, the carbon nanotube was positioned above a magnetic material containing several magnetization domains. The resulting magnetic stray field’s axis oscillates along the carbon nanotube length. For the confined electrons, this is equivalent to both a synthetic spin-orbit interaction and a Zeeman effect. This synthetic effect is evidenced in two ways. In a first experiment, we have measured the evolution of the nanotube’s energy levels when the magnetic material is progressively magnetized by an external magnetic field, thus destroying the oscillations of the stray field. In this experiment, the carbon nanotube had a very transparent contact to a superconducting metal, in addition to the synthetic spin-orbit interaction and Zeeman effect. These ingredients are a pre-requisite to observe Majorana quasiparticles in a one-dimensional nanoconductor. Those quasiparticles are under intense study for their potential use in quantum computing. In the second experiment, we have realized a double quantum dot in which each dot similarly lays above an oscillating magnetic field. The internal transitions of this DQD are measured with the microwave cavity signal. We evidenced a strong dispersion of the energy of the double quantum dots’ internal transitions with a small external magnetic field. This dispersion can be explained by a Zeeman effect in which the Landé factor, g, has been strongly renormalized by the synthetic spin-orbit interaction.
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  • HAL Id : tel-02535710, version 1

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Lauriane Contamin. Mise en évidence de textures de spin synthétiques par des mesures de transport et de champ microonde. Physique Quantique [quant-ph]. PSL Research University, 2019. Français. ⟨NNT : 2019PSLEE020⟩. ⟨tel-02535710⟩

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