arXiv subjects

Olfa Dani

Publications and source records attributed to Olfa Dani.

3 recordsLinked to original sources

arXiv2025

Interplay between Hund's rule and Kondo effect in a quantum dot

The interaction between localized spins on a quantum dot and free electrons in the reservoirs forms a many-particle entangled system giving rise to the Kondo effect. Here, we investigate electron transport in the third shell of a gate-defined GaAs quantum dot. The addition energy shows a maximum at half-filling of the shell which can be described analytically with Hund's rule exchange interaction. For 7 to 11 electrons occupying the quantum dot Zero-bias anomalies characteristic for the Kondo effect are observed, but with unexpected widths. Here the quantum dot has to be described as a multi-orbital Kondo impurity with Hund's interaction. In this way this quantum dot can be seen as a model system for a Hund's coupled mixed-valence quantum impurity as appearing in Hund's metals where local ferromagnetic interactions between orbitals lead to the emergence of complex electronic states.

cond-mat.mes-hall↗

arXiv2024

Direct measurement of spin-flip rates in single-electron tunneling

Spin-flips are one of the limiting factors for spin-based information processing. We demonstrate a transport approach for determining the spin-flip rates of a self-assembled InAs double quantum dot occupied by a single electron. In such devices, different Landé factors lead to an inhomogeneous Zeeman splitting, so that the two spin channels can never be at resonance simultaneously, leading to a spin blockade at low temperatures. This blockade is analyzed in terms of spin flips for different temperatures and magnetic fields. Our results are in good agreement with a quantum master equation that combines the dot-lead couplings with ohmic dissipation stemming from spin-flip cotunneling.

cond-mat.mes-hall↗

arXiv2022

Temperature-dependent broadening of coherent current peaks in InAs double quantum dots

Quantum systems as used for quantum computation or quantum sensing are nowadays often realized in solid state devices as e.g. complex Josephson circuits or coupled quantum-dot systems. Condensed matter as an environment influences heavily the quantum coherence of such systems. Here, we investigate electron transport through asymmetrically coupled InAs double quantum dots and observe an extremely strong temperature dependence of the coherent current peaks of single-electron tunneling. We analyze experimentally and theoretically the broadening of such coherent current peaks up to temperatures of 20 K and we are able to model it with quantum dissipation being due to two different bosonic baths. These bosonic baths mainly originate from substrate phonons. Application of a magnetic field helps us to identify the different quantum dot states through their temperature dependence.

cond-mat.mes-hall↗