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Soutenance de thèse

Lundi 20 Juin à 14h00,
Salle Rémy Lemaire, K223

Oratrice : Katrin ZIMMERMANN
"Quantum point contact in high mobility graphene"

Abstract

In the quantum Hall regime, the charge carriers are conducted within one-dimensional channels propagating at the edge of a two-dimensional electron gas (2DEG). A quantum point contact (QPC) device – a narrow constriction confining spatially electron transport – can control the transmission of these quantum Hall edge channels. In graphene, a QPC remains, however, challenging due to the formation of a pn-junction below the split gates along which electron and hole edge channels co-propagate and mix.

In this PhD thesis, we have fabricated ballistic graphene devices made by van der Waals stacking of hBN/Gr/hBN heterostructures, and equipped with split gates forming a QPC constriction. In the quantum Hall regime, the integer and fractional quantum Hall edge channels can be controlled and selectively transmitted by the QPC. Owing to the high mobility of our devices and the ensuing full lifting of the Landau level degeneracies in strong magnetic field, the mixing of edge channels at the pn-interface is restricted to sublevels of identical spins of the N=0 Landau level.

Furthermore, we will present tunnelling measurements between edge channels of the fractional quantum Hall effect which demonstrate the Luttinger liquid nature of these correlated one-dimensional channels in graphene.

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