Spin valves based on bilayer graphene quantum point contacts

Bernal bilayer graphene (BLG) is a unique material as it allows to open and electrostatically tune a sizeable band gap by applying a perpendicular electric field [1,2,3]. It has been demonstrated recently that it is possible to confine charge carriers in one dimension and form quantum point contacts (QPC) based on split gates separated by a channel of a few hundred nm [3]. Moreover, it has been shown that in such structures transport through a QPC can be spin-polarized up to 6 e²/h with a high in-plane magnetic field. The critical field at which the lowest modes are spin-polarized, depends on the subband spacing and thus on the width of the split gate channel. In this work, we combine two QPCs of different widths, resulting in different critical magnetic fields, so that we can spin-polarize the first QPC and use it as a filter for the second QPC. More precisely, we report on the realization of such a spin-valve, where we achieved a spin-polarized channel of up to 10 e²/h.

[1] E. McCann and M. Koshino, Rep. Prog. Phys. 76, 056503 (2013)

[2] S. Slizovskiy et al., Nano. Lett. 21, 6678 (2021)

[3] E. Icking et al., Adv. Electron. Mater., 2200510 (2022)

[4] H. Overweg et al., Nano. Lett. 18, 553 (2018)

[5] L. Banszerus et al., Phys. Rev. Lett. 124, 177701 (2020)