Impurity Dynamics in Tunable One-Dimensional Quantum Gases – IDTODQG

This project of an Austrian-French research collaboration is aimed at exploring, in a joint experimental and theoretical effort, the dynamics of impurities inside quantum wires of ultracold atoms. Mobile impurities inside a host medium constitute a paradigmatic physical system in condensed matter physics. In this project, using the toolbox of ultracold atomic quantum matter, we address the regime of impurities in one-dimensional geometry combined with strong interactions. This is the regime in which quantum effects dominate the static and dynamic properties in quantum wires. The project is aimed at exploring the impurity's driven motion and detecting interaction-induced oscillations, at investigating single-impurity diffusion and finding evidence for sub-diffusive quantum dynamics, at investigating the transition from repulsive to attractive interactions and using the impurity as a probe for novel quantum states, and at testing impurity dynamics in the presences of longitudinal lattice corrugations and exploring the regime of impurity pinning.

The experiments performed in Innsbruck by the Nägerl group will be tightly connected to theoretical modeling and analysis done by the Zvonarev group in Orsay. The project is based on ultracold bosonic atoms confined in tight tubular traps to mimic the impurity problem of condensed matter physics, making use of the excellent control over quantum states, confining geometry, and interactions together with nearly perfect isolation from external perturbations and high fidelity detection as provided by samples of ultracold atoms. The background “bath” atoms in the quantum wire are in one spin state, and the impurities are represented by single or few atoms that are in another spin state. The project will make use of tunable impurity-bath interactions to address a multitude of interesting questions about impurity dynamics in quantum wires: In which regime does the impurity resemble a classical particle in a viscous fluid? How does temperature affect the impurity's motion? Does integrability suppress impurity scattering and make its dynamics qualitatively different from the generic case? Does the periodic lattice potential lead to a band structure despite strong interactions? Could the impurity's motion be dissipationless? Our theoretical investigations are planned to be focused on the physical phenomena relevant for the experiments carried out within the project. We will use a broad spectrum of approaches existing for 1D quantum many-body systems: Bethe ansatz, effective field theories, and numerics (e.g. time-dependent density matrix renormalization group, tDMRG).

The planned outcome of the project is to gain a significantly deeper understanding of the basic physical principles that govern the dynamics in one-dimensional strongly-interacting quantum many-body systems. An understanding of such systems is of high relevance for future technological applications in view of the ongoing miniaturization of electronic wires towards lateral dimensions of atomic scales, where quantum many-body effects are expected to govern dynamics and transport and classical wires will become quantum wires.