QDev Seminar: Heidi Potts – University of Copenhagen

Heidi Potts

PostDoc, Solid State Physics, Lund University

Spin and orbital interactions in coupled QDs – from orbital Kondo to tunable g-factors

Parallel coupled quantum dots (QDs) offer an interesting platform to study the interaction of electrons and spins by quantum transport measurements. Recent advances in crystal phase engineering allow to create a QD consisting of a thin zinc-blende section between two wurtzite tunnel barriers in InAs nanowires [1]. Such a QD can be split into two parallel coupled QDs using two local sidegates and a global backgate. This system can be considered an artificial molecule, for which the electron population on the two dots can be changed separately, and the tunnel coupling between the two dots can be tuned [2-4].

In this work we study QDs with transparent tunnel barriers using co-tunneling spectroscopy. Our very recent results show the well-known spin-1/2 Kondo effect, the combined spin-orbital Kondo effect, and the isolated orbital Kondo effect when the spin-degeneracy is lifted with an external magnetic field. We further investigate co-tunneling transport as function of magnetic field to extract the g*-factor of 1-electron states. By hybridizing two orbitals we achieve g*-factors of up to 80. The g*-factor exhibits a large anisotropy under magnetic field rotation, which is a signature of the orbital contribution to it.

[1] M. Nilsson et al. PRB 93, 195423 (2016)
[2] M. Nilsson et al. Nano Letters 17, 7847 (2017)
[3] M. Nilsson et al. PRL 121, 156802 (2018)
[4] C. Thelander et al. PRB 98, 245305 (2018)