PhD in mesoscopic physics (M/F)

Job Description

Thesis Subject

High frequency noise for probing the properties of anyons

Your Work Environment

The mesoscopic physics group at LPENS is looking for a PhD candidate to study the properties of anyons using noise measurement techniques, with a particular focus on extending these techniques to the high-frequency regime where the measurement frequency is much larger than the thermal energy scale: hf ≫ k_BT.
Anyons are the elementary excitations of the fractional quantum Hall regime and are characterized by a fractional charge and fractional statistics. The latter property is particularly remarkable, as it implies that anyons do not belong to the two families of elementary particles found in 3D systems: bosons and fermions.
Over the years, the mesoscopic physics group has developed expertise in probing the properties of anyons by studying the current fluctuations generated by the partitioning of anyon beams at a quantum point contact (QPC) used as a beam splitter. For instance, the determination of the anyon fractional charge via noise measurements relies on accurately determining the slope of the noise evolution with respect to the backscattering current. However, the accuracy of this method is limited by its strict validity in the weak backscattering regime, where both the noise and backscattered currents become very small. While this technique is often extended to intermediate values of QPC transmission, such an extension is not straightforward for complex fractional quantum Hall states with intricate edge structures, where multiple edge channels propagate through the system. In these cases, the definition of transmission becomes ambiguous.
In contrast, high-frequency noise can reveal fractional charge and statistics in a more direct way, using a Josephson-type relationship between the voltage threshold V0 for the onset of high-frequency noise and the measurement frequency. This relationship depends on both the anyon fractional charge and fractional statistics when diluted beams of anyons are emitted toward the QPC. Although this approach allows for a more direct measurement of anyon properties, it suffers from a significant drawback that explains its limited use so far: due to the strong impedance mismatch between the high impedance of mesoscopic conductors and the 50-ohm RF cables, only a very small fraction of the photons emitted by the mesoscopic conductors are transmitted to the measurement cables. As a result, achieving a good signal-to-noise ratio requires very long measurement times.
To overcome this limitation, the successful applicant will develop a combination of impedance matching techniques and quantum-limited traveling wave parametric amplifiers to improve measurement efficiency. She/he will then apply radio-frequency (RF) noise measurements to characterize the properties of anyons associated with various fractional quantum Hall ground states, both abelian and non-abelian. The measurements will primarily focus on GaAs heterostructures, but an extension to graphene is also envisioned.

Constraints and risks

This position does not have any specific risks associated.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions