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Vivekanand TIWARI présente

Optical control and spin dynamics of an individual Cr in a semiconductor: Towards coherent mechanical driving with Surface Acoustic Waves

Mardi 9 novembre 2021 à 13h30 

Salle F-418, Institut Néel : jauge 15 personnes

Lien visio : https://smartvisio2.neel.cnrs.fr/b/luc-0bh-c8h

La présentation se fera en anglais


Résumé :

We studied a new single spin system with a large spin to strain interaction: an individual Cr atom in a CdTe quantum dot (QD). We first analyzed the spin dynamics of a Cr2+ using time-resolved optical pumping. We demonstrated that the spin relaxation of Cr is strongly sensitive to non-equilibrium phonons. We found excitation conditions where the prepared spin state can be preserved in the dark on a µs timescale. This opens the possibility to coherently control the Cr spin qubit with the resonant strain field of Surface Acoustic Wave (SAW). We designed and fabricated SAW transducers in the GHz range on ZnTe based structures. We demonstrated radio-frequency tuning of the energy of individual QDs by SAWs. Strain in the 10-4 range can be obtained. We also observed that the charge state of Cr could fluctuate. In particular, the negatively charged Cr+ ion, an excited state of the Cr in CdTe, can be stable when inserted in a QD. The Cr+ attracts a hole and form a stable hole-Cr+ complex with a ferromagnetic coupling. The ground states of the hole-Cr+ nano-magnet with Mz=±4 can be controlled by resonant optical pumping and a spin relaxation time in the 20 µs range is obtained.


La thèse a été réalisée sous la supervision de :
Lucien Besombes et Hervé Boukari

Les membres du jury sont :
Olivier Krebs (Rap.), DR CNRS, C2N, Palaiseau
Maria Vladimirova (Rap.), DR CNRS, Lab. Charles Coulomb, Montpellier
Benoit Eble, MdC Sorbonne Univ. INSP, Paris
Christopher Bauerle, DR CNRS, Institut Néel, Grenoble