Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: Quantum Dots and Wires: Transport (joint session HL/TT)

TT 21.5: Talk

Tuesday, March 18, 2025, 12:15–12:30, H13

Kondo effect for half-filling of the third shell of a quantum dot — •Olfa Dani¹, Johannes C. Bayer¹, Timo Wagner¹, Gertrud Zwicknagl², and Rolf J. Haug¹ — ¹1Institut für Festkörperphysik, Leibniz Universität Hannover, Hannover, Germany — ²2Institut für Mathematische Physik, Technische Universität Braunschweig, Braunschweig, Germany

In this work, we investigate the electrical transport in the third shell [1] of a gate-defined GaAs quantum dot. The exact number of electrons in the quantum dot (N_e) is determined using a quantum point contact as a sensitive charge detector, detecting single-electrons tunneling through the system [2]. N_e is varied by changing the applied gate voltage.

The addition energy E_c for N_e = 7 - 11 shows a triangular behavior with a maximum at half-filling of the shell. This observed behavior is described analytically with Hund’s rule exchange interaction. Besides, for successive numbers of electrons occupying the quantum dot N_e = 7 to 11, a Zero-bias anomaly (ZBA) characteristic for the Kondo effect is observed [3]. The width of the ZBA exhibits a triangular behavior, with a maximum at N_e = 9, similar to E_c. The broadening of the ZBA is attributed to the contribution of the Kondo resonance as well as Hund’s satellite peaks, originating from the degenerate orbitals observed in the spectral function.

[1] L. P. Kouwenhoven, et. al., Rep. Prog. Phys. 64, 701-736 (2001).

[2] T. Wagner, et. al., Nat. Phys.15, 330-334 (2019).

[3] J. Schmid, et. al., Phys. Rev. Lett. 84, 5824 (2000).

Keywords: Quantum Dots; Kondo Effect; Hund’s rule