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FM: Fall Meeting

FM 81: Enabling Technologies: Quantum Materials

FM 81.6: Talk

Donnerstag, 26. September 2019, 15:30–15:45, 3042

Large and tunable valley splitting in a ²⁸Si/SiGe quantum dot — •Tom Struck¹, Arne Hollmann¹, Veit Langrock¹, Andreas Schmidbauer², Floyd Schauer², Helge Riemann³, Nikolay V. Abrosimov³, Dominique Bougeard², and Lars R. Schreiber¹ — ¹JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Germany — ²Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Regensburg, Germany — ³Leibniz-Institut für Kristallzüchtung (IKZ), Berlin, Germany

²⁸Si has proven to be the host material of choice for electron spin qubits trapped in electrostatically defined quantum dots (QDs) [1,2]. A major challenge for Si/SiGe is the low valley splitting E_VS hampering qubit control. Here we investigate E_VS of a ²⁸Si/SiGe QD in a molecular-beam epitaxy-grown heterostructure with a residual ²⁹Si concentration of less than 60 ppm. We extract E_VS from the T₁ spin relaxation time as a function of magnetic field. We measure a large E_VS>200 µeV, which we can reproducibly tune by voltages applied to the depletion-gates. Investigating several mechanisms, we identify displacement of the QD with respect to atomistic details at the Si/SiGe interface as the dominant tuning mechanism.

[1]Yoneda, J. et al. A >99.9%-fidelity quantum-dot spin qubit with coherence limited by charge noise. Nature Nanotechnology 13,102-106(2017).
[2]Veldhorst, M. et al. A two-qubit logic gate in silicon. Nature 526, 410-414 (2015).