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Reference : UMR8023-GWEFEV-001
Workplace : PARIS 05
Date of publication : Wednesday, April 28, 2021
Scientific Responsible name : Gwendal FEVE
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 6 September 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Exchange statistics are related to the phase φ accumulated by the wavefunction describing the state of an ensemble of undistinguishable particles when two particles are exchanged. In the three-dimensional world, particles are divided between bosons, which obey φ=0 and tend to bunch together, and fermions, for which φ=π and which exclude each other via the Pauli exclusion principle. The situation is different in two-dimensional systems which allow the existence of quasiparticles called anyons with intermediate statistics between fermions and bosons, leading to intermediate degrees of bunching and exclusion. The strongly correlated phases of the fractional quantum Hall effect (FQH) have been predicted to host anyons carrying a fractional charge and obeying fractional statistics. The fractional charge has been observed twenty years ago by partitioning a beam of anyons and by measuring the resulting current noise, which is proportional to the fractional charge. However, despite numerous attempts, no direct signature of fractional statistics had been observed until two distinct experiments provided the first observations of fractional statistics this year. The first one performed by our consortium extended previous noise measurements in collider geometries to the FQH case in an anyon collider. Current noise measurements revealed the tendency of anyons to form larger charge packets in the collision process which is a signature of their intermediate exclusion statistics. The second experiment, performed by the Purdue group, observed braiding signatures in an anyon interferometer.
This PhD project aims at studying experimentally the quantum statistics of anyons using the anyon collider as a test bench for fractional statistics. More precisely, the project will focus on the realization of three different objectives. The first objective of the project is to quantitatively study the fractional statistics of anyons for different topological orders controlled by the filling factor. The second objective of the project is to understand the role of decoherence and relaxation on the experimental signatures of fractional statistics in the collider geometry. The third objective of the project is the quantitative study of the dynamical regime. Anyon emission will be triggered by time-dependent drives in order to control the synchronization of the arrival times of anyons on the beam-splitter. We will also investigate how the number of anyons colliding on beam-splitter can be controlled by varying the amplitude of the current pulses.
The PhD will take place at Laboratoire de Physique de l'ENS (24 rue Lhomond, 75005, Paris) within the mesoscopic physics team. The PhD student will be mainly supervised by the thesis director but will also benefit from the supervision of three other permanent researchers in the team. He or she may also benefit from interactions with other PhD students or postdoctoral researchers.
Constraints and risks
The PhD student will be confronted with very low temperature experiments involving the manipulation of cryogenic fluids (liquid nitrogen and helium).
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