OSCAR - Orbital & Spin currents in Cold Atom Rings

• Applicant: Professor Dr. Matteo Rizzi
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Theoretical Condensed Matter Physics
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277810020

Cooperative phenomena in many-particle systems have brought unique breakthroughs in scientific knowledge. For example, they enable accurate measurements of fundamental constants via the nearly exact quantization of the quantum Hall resistivity or via superconducting Josephson effects. These phenomena have also led to silent revolutions in every-day life, as in the case of the enormous data storage capacity offered by ferromagnetic hard-drives. In the increasingly important context of transport in nanostructures, however, many-body effects have not yet fully come to the fore, since they are often masked by uncontrolled disorder sources, complicated band-structure effects, and chemistry. In this project we plan to investigate the spin and orbital response of multi-component quantum gases, spurred by recent advancements in trapping and manipulating cold atoms in ring-shaped potentials. Progress in atomic, molecular, and optical physics (AMOP) has indeed consolidated the fact that cold atoms, controlled by quantum optical means, are an exceptionally tunable platform to study collective effects and cooperative phenomena beyond traditional condensed matter physics (CMP) limitations. The possibility of dealing with constituents of different statistical nature (bosons and fermions), the tailored realization of synthetic gauge potentials and coherent couplings, and the access to out-of-equilibrium physics, are just some of the most spectacular tools at disposal towards this aim.Here, we will focus on a nearly one-dimensional (1D) regime, where many-body effects are of paramount importance, and concentrate our efforts on:(i) the orbital magnetic susceptibility of 1D Dirac fermions in presence of interactions;(ii) the decay of spin currents due to many-body effects (e.g. spin drag), and the influence of statistics thereon;(iii) the impact of thermal fluctuations and disorder on these orbital and spin transport phenomena.Studying (i) may result in the discovery of extremely elusive states of matter: many-body orbital paramagnets. Research on cold atom spin currents as in (ii) may have important implications also on our understanding of spin transport in CMP setups such as spin-orbit-coupled semiconductor nanowires.Investigations will be conducted by employing powerful numerical techniques, based on the optimization of suitable Tensor Networks inspired by Density Matrix Renormalization Group schemes. Whenever possibile, our numerical analysis will be complemented by analytical approaches. Special attention will be devoted to the identification of "smoking guns" that are detectable by a combination of existing experimental protocols.We expect that this proposal will greatly advance our understanding of the subtle impact of many-body effects on "charge" and "spin" transport. We will answer fundamental questions and suggest dedicated cold atom experiments for the experimental testing of our predictions.

• DFG Programme: Research Grants
• International Connection: France, Italy
• Cooperation Partners: Professor Dr. Gerhard Birkl; Professor Dr. Frank Hekking (†); Professor Dr. Simone Montangero; Professor Dr. Roman Orus; Professor Marco Polini; Dr. Alessio Recati; Professor Jairo Sinova, Ph.D.