Nonlinear Acoustics in Ultracold Fermi Fluids
Abstract
Transport and out-of-equilibrium quantum dynamics provide some of the frontier problems in quantum many-body physics. An important example is the propagation of sound waves, which yield important information on a quantum system’s fundamental properties, such as its compressibility and diffusivities. Thanks to the advent of optical box traps for atoms, such physics has recently become experimentally accessible to ultracold fermion gases in settings of unprecedented cleanness. Indeed, there has been booming activity on sound in such systems, but they were essentially limited to the linear response regime. In the nonlinear regime of strong drives, new phenomena are expected to emerge, such as harmonic generation, self-interactions, and turbulence. Here we propose to broach the topic of nonlinear acoustics in ultracold Fermi fluids. The homogeneous density of gases confined in those traps and the sharp boundary conditions at their steep optical walls will allow us to create clean standing waves in the nonlinear regime and study their interactions. The homogeneity will be a game changer for density-dependent effects, which are crucial in nonlinear wave physics. Specifically, we will study the nonlinear density-density response of Fermi gases, in both weakly and strongly interacting regimes. We will measure for the first time the nonlinear susceptibility of the ideal Fermi gas, a fundamental but (remarkably) elusive quantity. Using moments of the density response, as well as spatial-mode tomography, we will experimentally reconstruct the nonlinear wave equation governing the acoustics of the strongly interacting Fermi gas. This will yield novel information on the rich problem of microscopic interactions between phonons in such a strongly correlated system. This program is motivated by recent experimental surprises that we have made, pointing to richer physics than anticipated.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 07, 2024
- Source ID
- FA95502310605
Entities
People
- Nir Navon
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- Yale University