Bose-Einstein condensation of atoms in a uniform potential (1212.4453v1)

Abstract: We have observed Bose-Einstein condensation of an atomic gas in the (quasi-)uniform three-dimensional potential of an optical box trap. Condensation is seen in the bimodal momentum distribution and the anisotropic time-of-flight expansion of the condensate. The critical temperature agrees with the theoretical prediction for a uniform Bose gas. The momentum distribution of our non-condensed quantum-degenerate gas is also clearly distinct from the conventional case of a harmonically trapped sample and close to the expected distribution in a uniform system. We confirm the coherence of our condensate in a matter-wave interference experiment. Our experiments open many new possibilities for fundamental studies of many-body physics.

• The paper demonstrates the experimental realization of BEC in a uniform potential, evidenced by bimodal momentum distribution and interference patterns.
• The paper employs an optical box trap to remove harmonic trap biases, achieving a critical temperature of around 90 nK and an effective r^(13±2) potential.
• The findings pave the way for precise studies of quantum critical phenomena and improved atom interferometry in many-body physics.

Bose-Einstein Condensation in a Uniform Potential: A Detailed Analysis

The paper, "Bose-Einstein condensation of atoms in a uniform potential," by Gaunt et al., addresses a critical advancement in the experimental investigation of many-body quantum systems. It reports the observation of Bose-Einstein condensation (BEC) within a three-dimensional quasi-uniform potential, distinct from the standard harmonic traps conventionally used. The authors employed an optical box trap to realize this uniform potential, facilitating a more direct paper of fundamental properties of quantum-degenerate gases without the biases introduced by confining geometries.

Experimental Approach and Findings

The experimental setup employed $^{87}$Rb atoms initially cooled in a harmonic trap before being transferred to an optical box trap for further evaporation into a BEC state. Critical observations include:

1. Condensate Evidence: Condensation was evident from a bimodal momentum distribution and anisotropic time-of-flight (TOF) expansion, meeting theoretical predictions for a uniform Bose gas concerning critical temperature ($T_c \approx 90\;$nK) and momentum distribution.
2. Characterization and Validation: Importantly, the momentum distribution of the non-condensed atoms diverged from that observed in harmonic traps, instead aligning closely with theoretical expectations for a truly uniform system. Coherence of the condensate was confirmed through matter-wave interference experiments.
3. Trap Potential Analysis: An effective $r^{13\pm2}$ potential was determined from momentum distribution and thermal fits, suggesting minimal deviation from an ideal flat potential.

Implications for Many-Body Physics

The experimental realization of BEC in a uniform potential demonstrates several substantial implications:

• Critical Phenomena Studies: The uniform potential allows exploration of systems as they approach quantum critical points, providing clearer insights into Kibble-Zurek mechanisms and phase transitions without the complications of local density influences.
• Interaction Studies: The lower density of the condensate compared to traditional harmonic traps reduces three-body loss rates; this potentially enables more precise investigations at and beyond unitarity, particularly near Feshbach resonances.
• Interferometry Advancement: With lower density and longer coherence times, the uniform trap design holds promise for enhanced sensitivity in atom interferometry applications, crucial for precision measurements and fundamental physics tests.

Future Directions

Gaunt et al.'s experiment introduces a framework with immense potential for fundamental physics studies. Future research directions may include:

• Strongly Interacting Bose Gases: Investigating ground state properties and dynamics in the strongly interacting regime to understand superfluid behavior and beyond mean-field physics.
• Topological and Superfluid Transitions: Exploring how the reduced trap-induced perturbations affect transition dynamics in systems with nontrivial topology or coupled external fields.
• Integration with Optical Lattices: Combining uniform BEC with optical lattice potentials could revolutionize studies of Hubbard models and quantum magnetism.

This research lays foundational experimental advancements for delving deeper into many-body physics and promises further refinement in the manipulation and understanding of quantum-degenerate systems.