Description du sujet de thèse

Superfluidity is a striking collective behavior of quantum fluids, characterized by a vanishing viscosity and frictionless flow, leading to features such as persistent currents, quantized vortices, and critical velocities for flow stability. In low dimensions however, and particularly in one-dimensional geometries, quantum fluctuations have an enhanced role, leading to significant differences compared to higher dimensional ones, such as the predictions of a non-zero quantum friction force existing any flow velocity. The competition between this quantum friction force and the quasi long-range order in the system at low temperatures question the 'standard' definitions of superfluidity.
The experimental PhD project is based on an existing potassium Bose-Einstein experiment, and is aimed towards exploring the superfluid transport properties of low-dimensional ultracold atomic Bose gases confined in optical ring traps. One of the first goals of the PhD project is to implement optical traps designed to confine atomic Bose-Einstein condensates in tightly focused optical ring potentials. These potentials create a one-dimensional regime for quantum gases, enabling the study of superfluidity in conditions where 'standard' mean-field theory is insufficient, and quantum fluctuations dominate. The strongly-interacting regime will be explored using the interplay between strong optical confinement and large interactions enabled by Feshbach resonances.
Once implemented, these techniques will be aimed at characterizing critical speeds for superfluidity, excitation dynamics, and the role of quantum coherence. Ultimately, these developments will allow the investigation of 1D superfluidity beyond the mean-field regime and guide future theoretical directions beyond the current state-of-the-art.
The project is mainly experimental, and involves ongoing collaborations with theory experts in the field. The PhD funding is secured through an ANR project and the IKS graduate program.

[1] RMP 94, 041001 (2022) - Atomtronic circuits: From many-body physics to quantum technologies
[2] PRA 85, 053627(2012) - Probing superfluidity of a mesoscopic Tonks-Girardeau gas
[3] PRA 91, 063619 (2015) - Dynamic structure factor and drag force in a one-dimensional strongly interacting Bose gas at finite temperature

Contexte de travail

The Quantum Systems team at the PhLAM laboratory enjoys international recognition for its work on ultracold atom physics, particularly on disordered and chaotic dynamical quantum systems. The team has recently developed a new experimental setup for Bose-Einstein condensation with potassium atoms, which will enable the study of novel phenomena related to superfluidity in low dimensions.
PhD supervisor: Radu Chicireanu
Location: PhLAM Laboratory, Building P5, Cité Scientifique campus in Villeneuve-d'Ascq (near Lille, France).

Contraintes et risques

Requirements:
- Master's degree (or equivalent – 5 years of university-level education)
- Knowledge of quantum mechanics and solid-state physics
- Experience in an experimental physics laboratory