Observation of quantum Hall interferometer phase jumps due to a change in the number of bulk quasiparticles

Abstract

We measure the magneto-conductance through a micron-sized quantum dot hosting about 500 electrons in the quantum Hall regime. In the Coulomb blockade, when the island is weakly coupled to source and drain contacts, edge reconstruction at filling factors between one and two in the dot leads to the formation of two compressible regions tunnel coupled via an incompressible region of filling factor ν = 1. We interpret the resulting conductance pattern in terms of a phase diagram of stable charge in the two compressible regions. Increasing the coupling of the dot to source and drain, we realize a Fabry-Pérot quantum Hall interferometer, which shows an interference pattern strikingly similar to the phase diagram in the Coulomb blockade regime. We interpret this experimental finding using an empirical model adapted from the Coulomb blockaded to the interferometer case. The model allows us to relate the observed abrupt jumps of the Fabry-Pérot interferometer phase to a change in the number of bulk quasiparticles. This opens up an avenue for the investigation of phase shifts due to (fractional) charge redistributions in future experiments on similar devices. :1910.12525v1 [cond-mat.mes-hall] arXiv

Fractional Coulomb blockade for quasi-particle tunneling between edge channels

“…The evolution from the distinct pattern at ν dot = 2 in Fig. 4A toward filling factor 1 has been studied in detail in previous work ( 37 ) and is found here to behave in the same way. For a regime 1 > ν dot ≳ 0.75, the Coulomb resonances show no periodic modulations as seen in Fig.…”

“…3A as a function of magnetic field B for the regions where periodic modulations are observed. We find a stable period of Δ B = 5.6 mT (corresponding to an area ) at ν dot ≈ 2 (blue dots) slowly rising toward and diverging at ν dot ≈ 1, which is directly related to the decreasing area enclosed by the incompressible ν in = 1 stripe as the upper spin-split branch of the lowest Landau level is depopulated ( 37 ). For ν dot ≳ 2/3 (green squares), the period quickly increases with increasing B as well.…”

“…To further study the modulated Coulomb oscillations at filling factor ν dot ≳ 2/3 and get quantitative predictions, we extend the model for the integer quantum Hall effect discussed in our previous work ( 37 ) to fractional filling factors. We assume the existence of two compressible regions for the fractional filling factor ν dot ≳ 2/3 separated by an incompressible ν in = 2/3 region as schematically depicted in Fig.…”

“…Regions of stable charge (N 1 and N 2 ) (separated by white lines in Fig. 2A) can be described by a capacitance model (33,35,37,44) where N 1 and N 2 correspond to the number of electrons on the outer and inner compressible region, respectively. Changing to the fractional quantum Hall regime, the conductance depending on the magnetic field and the PG voltage is shown in Fig.…”

“…As each compressible region forms a QD, the quasi-particle tunneling can be treated in a capacitive single particle model as the fractional Coulomb blockade between two nested QDs. We construct a phase diagram of stable charge, which was previously proposed theoretically ( 44 ) and measured for integer Landau levels ( 37 , 45 – 50 ).…”