September 2019

Abstracts of the QSIT Lunch Seminar, Thursday, September 5, 2019

Diamond Tips for Scanning NV Magnetometry

Gabriel Puebla-Hellmann - QZabre and Spin Physics group (Degen group), ETH Zurich

Scanning Nitrogen Vacancy Center Magnetometry is a recently established, powerful technique to quantitavely image magnetic fields at the nanometer scale.
Based on a measuring the optically detected magnetic resonance of an NV center scanning over a surface, it can provide novel insight into materials such as antiferromagnets, and other physical phenomena, such as viscous electron transport in graphene.
This talk will cover the underlying principles and example applications as well as the intricacies involved in creating and optimizing the key component, the diamond scanning tip.

Electrostatically-Defined Quantum Dots in Bilayer Graphene

Annika Kurzmann - Nanophysics group (Ensslin group), ETH Zurich

Graphene is a promising candidate for future nano-electronic devices including building blocks for quantum information processing. Recent improvements in fabrication technologies for graphene nanostructures and the use of electrostatic gating of bilayer graphene, have leveraged the quality of quantum dots to such an extent, that few-electron or -hole quantum dots have been realized [1].
We use finite bias spectroscopy to study and identify the single-particle and many-body ground- and excited states of electrostatically defined quantum dots in bilayer graphene trapping only one or two charge carriers [2]. Our experiments allow us to propose a remarkably clear level scheme for the two-particle spectra, in which the spin- and valley-entanglement, as well as exchange interactions play a crucial role. With this level scheme at hand, future experiments can investigate spin- and valley-coherence and relaxation times, which are key parameters to be compared to other material systems.

References
[1] M. Eich, R. Pisoni, H. Overweg, A. Kurzmann, Y. Lee, P. Rickhaus, F. Herman, M. Sigrist, K. Watanabe, T. Taniguchi, T. Ihn and K. Ensslin, Phys. Rev. X 8, 031023 (2018).
[2] A. Kurzmann, M. Eich, H. Overweg, M. Mangold, P. Rickhaus, R. Pisoni, Y. Lee, R. Garreis, C. Tong, K. Watanabe, T. Taniguchi, K. Ensslin, and T. Ihn, Phys. Rev. Lett. 123, 026803 (2019).