Theory of spin and valley lifetimes in bilayer graphene quantum dots

The low nuclear spin density and weak spin-orbit coupling found in graphene allows for long electron spin relaxation and coherence times. The spin and valley degrees of freedom of localized electrons can therefore be seen as potential embodiments of classical or quantum bits for computation [1,2]. However, the formation of localized states in quantum dots requires some form of badgap engineering, and the mechanisms for spin and valley relaxation have so far not been completely understood. Bilayer graphene has an electrically controllable bandgap that allows for the formation of electrostatically defined quantum dots. We present theoretical considerations regarding the formation of quantum dots in graphene and report on recent progress in understanding the relevant physical mechanisms of spin and valley relaxation in electrostatically gated bilayer graphene quantum dots [3]. We then compare theoretically obtained spin and valley relaxation times and their dependence on the applied magnetic field with the latest experimental data [4,5,6].

[1] B. Trauzettel, D.V. Bulaev, D. Loss, and G. Burkard, Nature Phys. 3, 192 (2007).

[2] M. Droth and G. Burkard, Spintronics with graphene quantum dots, Phys. Status Solidi RRL 10, 75 (2016).

[3] L. Wang and G. Burkard, manuscript in preparation (2023).

[4] L. M. Gächter, R. Garreis, et al., PRX Quantum 3, 020343 (2022).

[5] L. Banzerus, K. Hecker, et al., Nature Comm. 13, 3637 (2022).

[6] R. Garreis, C. Tong, et al., arXiv:2304.00980 (2023).