Emergent quantum Hall ground states driven by proximity exchange coupling in 2D material/ferromagnet interfaces*

In hBN/Graphene/EuS layer system we observe phase transitions spanning various quantum Hall regimes from quantum spin Hall edge state to anti-ferromagnetic state via an intermediate canted anti ferromagnetic (CAF) state. This is first demonstration of quantum Hall ferromagnetic ground states driven by proximity coupling with a ferromagnetic insulator (resulting in a huge exchange field) and achieved at a much lower applied magnetic field than any study in the past. The results clearly demonstrate the opening of edge state corresponding to CAF gap, while at much higher fields we observe reentrant insulating phase corresponding to the bulk gap as predicted by theory [1]. We also investigate the effects with WS2/Graphene/EuS stack. This led to interesting ground states emerging as a result of ferromagnet and SOC coupling induced by proximity effects. In this talk we will discuss the details of emergent ground state in 2D material/Ferromagnet interface effects along with future direction.

1. Kharitonov, M. PRL 109, 046803 (2012), PRB 85, 155439 (2012), PRB 86, 075450 (2012)