Towards an understanding of transport through junctions in
quantum-Hall systems
by
Siddharta Lal(ASICTP Trieste)
→
Europe/Stockholm
FA31
FA31
Description
Motivated by recent experimental findings (e.g., Roddaro et al.,
PRL 95, 156804 (2005)), we study transport in a simple phenomenological
model of a quantum Hall edge system with a gate-voltage controlled
constriction lowering the local filling factor. The current backscattered
from the constriction is seen to arise from the matching of the properties
of the edge-current excitations in the constriction ($\nu_{2}$) and bulk
($\nu_{1}$) regions. We develop a hydrodynamic theory for bosonic edge
modes inspired by this model, finding that a competition between two
tunneling process, related by a quasiparticle-quasihole symmetry,
determines the fate of the low-bias transmission conductance. A novel
generalisation of the Kane-Fisher quantum impurity model is found,
describing transitions from a weak-coupling theory at partial transmission
to strong-coupling theories for perfect transmission and reflection as
well as a new symmetry dictated fixed point. These results provide
satisfactory explanations for many recent puzzling experimental results at
filling-factors of 1/3 and 1.
