Quantum Anomaly and 2D-3D Crossover in Strongly Interacting Fermi Gases

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Gases
• Condensed Matter Physics

Background:

• Collective oscillations in trapped quantum gases provide insights into their thermodynamic properties.
• The transition from two-dimensional (2D) to three-dimensional (3D) systems offers a unique platform to study dimensionality effects on quantum phenomena.

Purpose of the Study:

• To experimentally investigate collective oscillations, specifically the breathing mode, in harmonically trapped Fermi gases across the 2D to 3D crossover.
• To probe the equation of state and explore the impact of tunable interactions and dimensionality on system dynamics.

Main Methods:

• Measurements of the radial monopole oscillation (breathing mode) frequency in highly oblate Fermi gases.
• Tuning interatomic interactions and atom number to control the chemical potential and explore the 2D to 3D crossover.
• Comparison of experimental results with theoretical predictions, including scale-invariant models and quantum anomaly considerations.

Main Results:

• Breathing mode frequencies were measured in Fermi gases transitioning from 2D to 3D.
• Measurements deep in the 2D regime exceeded the prediction of scale-invariant dynamical scaling, providing evidence for a quantum anomaly.
• The observed frequencies demonstrate a smooth evolution between the 2D and 3D thermodynamic limits as atom number is varied.

Conclusions:

• The experimental results indicate a breakdown of the elementary delta-potential model for atomic interactions in the 2D regime.
• The study provides evidence for the quantum anomaly in 2D Fermi gases, highlighting the importance of quantum effects and renormalized interactions.
• The work establishes a connection between collective oscillation frequencies and the thermodynamic equation of state across different dimensions.