Invited Paper 2D+EM+MI+MN+NS-TuA3
Quantum Devices with 2D Materials

Tuesday, October 23, 2018, 3:00 pm, Room 201B

Quantum dots in graphene have been mostly realized by etching. This leads to localized states at the uncontrolled edges dominating the transport properties of these quantum devices. [1] It is well known that in bilayer graphene gaps can be opened by vertical electrical fields. [2] This approach has been used with limited success to define quantum devices [3]. The pinch-off characteristics are typically limited by leakage currents often thought to occur at the physical sample edges [4].

Here we demonstrate that electrostatically tunable barriers can be fabricated on bilayer graphene devices with graphite as a back gate. We measure pinch-off resistances exceeding GOhms and observe quantized conduction plateaus for one-dimensional constrictions. [5] With suitable gate arrangements few carrier hole and electron quantum dots can be electrostatically defined. We measure the controlled occupation of quantum dots with single holes and electrons. Four-fold level bunching is observed in Coulomb blockade spectroscopy which is understood in terms of valley and spin states. Magnetic field dependence allows to investigate orbital and spin/valley degrees of freedom.

We further demonstrate quantum devices build on MoS2.

1. For a review see Bischoff et al., Applied Physics Reviews 2, 031301 (2015)

2. Oostinga et al., Nat. Materials 7, 151 (2007)

3. Allen et al., Nat. Comm. 3, 934 (2012)

4. [https://www.nature.com/articles/ncomms14552#auth-1] et al., Nat. Comm. 8, 14552 (2017)

5. Overweg et al., [https://arxiv.org/abs/1707.09282], [https://arxiv.org/abs/1709.00870]