Universal Tetramer and Pentamer Bound States in Two-Dimensional Fermionic Mixtures.

Area of Science:

• Quantum physics
• Few-body physics
• Cold atom systems

Background:

• Investigating few-body bound states in 2D systems is crucial for understanding emergent phenomena.
• The (N+1) system with heavy fermions and a light atom provides a tunable platform for studying universal physics.

Purpose of the Study:

• To determine the critical heavy-light mass ratios for the emergence of universal tetramer (3+1) and pentamer (4+1) bound states.
• To analyze the density distributions and momentum-space correlations of these few-body bound states.
• To explore the experimental accessibility of these states in cold atom laboratories.

Main Methods:

• Theoretical analysis of the (N+1) system.
• Calculation of critical mass ratios for bound state formation.
• Investigation of few-body correlations in momentum space.

Main Results:

• The critical mass ratio for a (3+1) tetramer below the trimer threshold is 3.38.
• The critical mass ratio for a (4+1) pentamer below the tetramer threshold is 5.14.
• Ground state tetramers and pentamers, despite zero total angular momentum, show distinct density and momentum correlations due to their internal angular momentum structures.

Conclusions:

• Universal tetramer and pentamer bound states exist in the studied 2D system.
• These states are characterized by specific critical mass ratios and unique correlation patterns.
• The findings suggest experimental realization in Fermi-Fermi mixtures and highlight the importance of few-body correlations in many-body systems.