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Résumé |
Under strong magnetic fields, electrons that are confined to two spatial
dimensions can ex-hibit a fractional quantum Hall state where the elementary
particles carry only a fraction of the electron charge. These exotic
excitations, called anyons, moreover behave under the in-terchange of two
individuals neither as fermions nor as bosons but are characterized instead by a
non-trivial exchange phase. The experimental proof of these anyons and their
exchange phase was performed only recently, in 2020. Recent experiments have
notably demonstrated that a quantum point contact on the edge channels of a
fractional quantum Hall (Laughlin) state is able to reveal the anyonic phase
from noise measurements.
After introducing anyons in the fractional quantum Hall effect, we will explore
their imprint along the edge of the system and their manipulation using quantum
constrictions. Focusing on the tunneling of anyons at a quantum point contact,
we will show how this process is partly governed by a 1+1 space-time braiding
mechanism between anyons. This mechanism mirrors the conventional anyonic
braiding observed when a quasiparticle adiabatically en-circles another. The
braiding phase can then be extracted from correlated noise measure-ments at the
output of series of quantum point contacts where the non-linearity of tunneling
also plays a significant role. We shall also discuss Andreev tunneling at a
quantum con-striction, which involves the conversion of anyons to electrons or
between different types of anyons. This process leaves a distinctive signal on
the cross-correlation, and has also re-ceived experimental confirmation. |
