Bias controlled switching of spin polarization between ν = ±1 quantum Hall edges at graphene pn junction
ORAL
Abstract
Differentiating between the ground states of the half-filled zeroth Landau level in graphene is the key to
understand their low-energy excitations. One promising route for this is to study the effects of different
ground states of ν = 0 filling on nearby edge states belonging to fillings |ν| > 0. In this regard, graphene
pn junction is an ideal platform, as in the symmetry broken quantum Hall (QH) regime, the co-propagating
electron and hole-like edge states at the junction are separated by a narrow ν = 0 region. Here, we report
bias controlled tunneling between ν = ±1 QH edges in a graphite gated hBN encapsulated monolayer
graphene device. At zero bias, we observe finite tunneling (t ∼ 0.5), which remains almost constant up
to ∼ 120μV at 8T. Strikingly, above ∼ 120μV the tunnelling sharply falls and exhibits repeated smaller
peaks at discrete energies before vanishing completely. Moreover, the tunneling shows unique dependence
on filling, magnetic field and temperature. The tunneling at zero bias is anomalous as it is is expected to
be zero between ν = ±1 edges due to their orthogonal spin polarization. Thus, from tunneling to fully
blockade suggests bias-controlled switching of spin polarization between ν = ±1 edges, which is further
corroborated with our detailed theoretical calculations.
understand their low-energy excitations. One promising route for this is to study the effects of different
ground states of ν = 0 filling on nearby edge states belonging to fillings |ν| > 0. In this regard, graphene
pn junction is an ideal platform, as in the symmetry broken quantum Hall (QH) regime, the co-propagating
electron and hole-like edge states at the junction are separated by a narrow ν = 0 region. Here, we report
bias controlled tunneling between ν = ±1 QH edges in a graphite gated hBN encapsulated monolayer
graphene device. At zero bias, we observe finite tunneling (t ∼ 0.5), which remains almost constant up
to ∼ 120μV at 8T. Strikingly, above ∼ 120μV the tunnelling sharply falls and exhibits repeated smaller
peaks at discrete energies before vanishing completely. Moreover, the tunneling shows unique dependence
on filling, magnetic field and temperature. The tunneling at zero bias is anomalous as it is is expected to
be zero between ν = ±1 edges due to their orthogonal spin polarization. Thus, from tunneling to fully
blockade suggests bias-controlled switching of spin polarization between ν = ±1 edges, which is further
corroborated with our detailed theoretical calculations.
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Presenters
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Arup K Paul
- Indian Institute of Science Bangalore