Controlling spin-orbit interactions in silicon quantum dots using magnetic field direction

Silicon-based quantum dots are considered as an excellent platform for spin qubits partly thanks to the weak spin-orbit interaction (SOI) of the electrons occupying the dots. However, the symmetry reduction at the sharp interface in the heterostructure induces relatively strong SOI. This interaction can vary between the devices and even from dot to dot in the same device [1]. SOI can either be employed as a powerful tool or it can degrade the performance of the qubits. For instance SOI enables driving electron spin resonance (ESR) electrically without micromagnet and is responsible for the variation in the g-factors between dots that enable individual addressability. However, in some cases it would preferable to turn on SOI for instance to drive global ESR, to exclude the decoherence caused by the Stark shift or to turn off the mixing between S-T- states [2,3,4]. In this work, we study experimentally SOI with the external magnetic field in a silicon MOS double dot system [5]. We demonstrate tunability of g-factor difference, Stark effect, S-T- mixing and show that we can turn them off on demand. We also extract the full g-tensor of both of the dots and demonstrate the increase of coherence time that we attribute the reduced decoherence due to the vanishing Stark shift. We conclude that the tunability in the SOI provides intriguing new ways of operating silicon spin qubits.

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2. A. Hofmann, V. F. Maisi, T. Krähenmann, C. Reichl, W. Wegscheider, K. Ensslin, and T. Ihn, Phys. Rev. Lett. 119, 176807, (2017).
3. R. Ferdous, K. W. Chan, M. Veldhorst, J. C. C. Hwang, C. H. Yang, G. Klimeck, A. Morello, A. S. Dzurak, and R. Rahman, Phys. Rev. B 97, 241401 (2018).
4. R. Ruskov, M. Veldhorst, A. Dzurak, and C. Tahan, arXiv: 1708.04555 (2017).
5. T. Tanttu, B. Hensen, K. W. Chan, H. Yang, W. Huang, M. Fogarty, F. Hudson, K. Itoh, D. Culcer, A. Laucht, A. Morello, A. Dzurak, arXiv: 1807.10415 (2018)