Regensburg 2019 – scientific programme

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SYIS: Symposium Interactions and Spin in 2D Heterostructures

SYIS 1: Interactions and Spins in 2D Heterostructures

SYIS 1.5: Invited Talk

Thursday, April 4, 2019, 17:15–17:45, H1

Flipping the valley in graphene quantum dots — •Markus Morgenstern — II. Institute of Physics B, RWTh Aachen University, 52074 Aachen

Graphene provides two extra binary degrees of freedom, - sublattice and valley -, dubbed pseudospins. They might offer additional possibilities for information processing.

Via low-temperature STM measurements, I will demonstrate the control of the valley pseudospin within an edgeless graphene quantum dot (QD) on BN. The QD is induced by the potential of the STM tip [1]. An external B field provides the required gaps by Landau quantization. As such, the QD can be moved freely across the graphene/BN sample. The laterally changing orientation of the C atoms with respect to B and N changes the valley splitting of the confined states continuously [2]. This eventually leads to an inversion, i.e., an individuial electron is flipped from one valley to the other.

Compelling evidence for the flipping process is provided by favorable quantitative comparison with calculations based on density functional theory.

Additionally, I will pinpoint to the control of the sublattice degree of freedom by huge pseudomagnetic fields (~1000 T) caused by the van-der Waals forces of the STM tip [3].

[1] N. Freitag et al., Nano Lett., 16, 5798 (2016). [2] N. Freitag et al., Nat. Nanotechnol. 13, 392(2018). [3] A. Georgi et al., Nano Lett., 17, 2240 (2017).