insight - Scientific Computing - # Ultracold Atomic Physics

Characterization of Temperature-Dependent Three-Body Loss in Erbium-166 and Optimization of Large Bose-Einstein Condensate Production

Q: How might the understanding of these temperature-dependent loss features be applied to other elements or isotopes within the lanthanide series?

The observation of temperature-dependent three-body loss features in ${}^{166}$Er, potentially linked to resonant trimer states, offers valuable insights applicable to other lanthanide atoms like Dy, Tm, and Yb. These elements share similar electronic structures and strong dipole-dipole interactions, suggesting that analogous loss features might exist. Here's how the understanding can be applied: Predicting Loss Features: The resonant trimer model, if validated, could predict the positions and temperature dependencies of loss features in other lanthanides. This would require spectroscopic data on the molecular potentials and scattering properties of these atoms. Optimizing Cooling and Trapping: Knowledge of loss features is crucial for optimizing evaporative cooling and maximizing atom numbers in degenerate quantum gas experiments. By avoiding magnetic field regions with high three-body loss rates, one can enhance the efficiency of cooling and achieve larger atom numbers. Exploring Few-Body Physics: The temperature dependence of these loss features provides a way to probe the underlying few-body physics governing ultracold collisions in lanthanide atoms. By systematically studying the loss rates as a function of temperature and magnetic field, one can gain insights into the nature of the resonant trimer states and their coupling to the scattering continuum. However, it's important to note that the specific positions and characteristics of these loss features will depend on the detailed atomic and molecular properties of each element and isotope. Further experimental and theoretical investigations are needed to fully explore and exploit these phenomena in other lanthanide systems.

Q: Could the presence of these loss features be exploited for the controlled manipulation or study of specific few-body quantum states?

Yes, the presence of these temperature-dependent loss features, attributed to resonant trimer states, opens up intriguing possibilities for manipulating and studying few-body quantum states in ultracold lanthanide gases. Here are some potential avenues: State-Selective Loss: By tuning the magnetic field to a specific loss feature, one could selectively remove atoms in a particular three-body state. This could be used to prepare the system in a desired initial state for further experiments or to study the dynamics of few-body correlations. Trimer Spectroscopy: The loss features themselves can be viewed as a form of trimer spectroscopy, providing information about the energies and lifetimes of these bound states. By carefully measuring the positions, widths, and temperature dependencies of the loss features, one can extract valuable information about the underlying three-body interactions. Controlled Molecule Formation: Three-body recombination, the process responsible for the loss features, can also lead to the formation of diatomic molecules. By controlling the magnetic field and temperature, one could potentially enhance molecule formation rates and study the properties of these molecules. However, exploiting these loss features for controlled manipulation requires precise control over magnetic fields and temperatures, as well as a thorough understanding of the underlying three-body physics. Further experimental and theoretical efforts are needed to fully realize the potential of these features for manipulating and probing few-body quantum states.

Q: If we consider the analogy of a crowded room emptying more slowly than expected, what other factors beyond individual interactions might contribute to the observed "stickiness" of the erbium atoms at specific energy levels?

The analogy of a crowded room emptying slowly is apt for describing the reduced loss rate between the resonant features. While individual two-body interactions would dictate a certain "exit rate," the collective behavior due to the dipolar interactions in erbium leads to unexpected "stickiness." Here are some factors contributing to this: Dipolar Interactions and Correlations: Erbium atoms interact via long-range and anisotropic dipole-dipole forces. These interactions can lead to the formation of correlated many-body states, even in the thermal gas. These correlations can hinder the formation of the resonant trimer states, effectively reducing the three-body loss rate. Quantum Statistics: Erbium atoms are bosons, and at ultracold temperatures, their quantum statistics become important. The Pauli exclusion principle for bosons can influence the occupation of energy levels and affect the formation of trimer states. Energy Dependence of Interactions: The strength and nature of the interatomic interactions can depend on the relative energy between the atoms. At specific energies corresponding to the resonant trimer states, the interactions are enhanced, leading to increased loss. However, away from these resonances, the interactions might be weaker, resulting in reduced loss rates. Trapping Potential: The confining potential of the optical trap can also play a role. The trap geometry and anisotropy can influence the spatial distribution of the atoms and modify the effective strength of the interactions, thereby affecting the loss rate. In essence, the "stickiness" arises from the interplay of dipolar interactions, quantum statistics, and the energy dependence of interactions. These factors can lead to collective behavior that modifies the simple picture of independent three-body collisions, resulting in the observed suppression of loss rates between the resonant features.

Core Concepts

This research paper details the discovery and characterization of previously unreported temperature-dependent three-body loss features in erbium-166, and how this knowledge was used to optimize the production of large Bose-Einstein condensates.

Abstract

Bibliographic Information: Krstajić, M., Juhász, P., Kučera, J., Hofer, L. R., Lamb, G., Marchant, A. L., & Smith, R. P. (2024). Characterisation of three-body loss in 166Er and optimised production of large Bose-Einstein condensates. arXiv preprint arXiv:2307.01245v2.
Research Objective: This study aimed to investigate the three-body loss dynamics in ultracold erbium-166 gas and utilize this understanding to optimize the production of large Bose-Einstein condensates (BECs).
Methodology: The researchers trapped ultracold erbium-166 atoms in an optical dipole trap and systematically measured the atom loss rates at various magnetic field strengths and temperatures. They analyzed the loss features and their temperature dependence, fitting the data to theoretical models. Based on their findings, they developed an optimized evaporative cooling sequence to maximize BEC production.
Key Findings: The study identified six previously unreported loss features in the three-body loss spectrum of erbium-166 at magnetic fields below 4 G. These features exhibited a strong temperature dependence, broadening and shifting to higher magnetic fields with increasing temperature. The researchers observed a linear relationship between the peak width and position of these loss features with temperature. They also found a polarization-dependent shift in the loss features with the intensity of the optical trap laser light.
Main Conclusions: The observed temperature dependence of the loss features is consistent with a "resonant trimer" model, suggesting the formation of transient three-atom bound states. By carefully mapping the loss landscape, the researchers were able to optimize the evaporative cooling process, minimizing atom loss and maximizing the production of large BECs containing over 2 x 10^5 atoms.
Significance: This research provides valuable insights into the complex interplay of interactions in ultracold dipolar gases. The discovery of new loss features and their characterization enhances the understanding of three-body loss mechanisms in lanthanide atoms. The optimized BEC production technique paves the way for future studies of exotic quantum phases in large-atom-number dipolar gases.
Limitations and Future Research: The study primarily focused on a specific magnetic field range below 4 G. Further investigations at higher magnetic fields and different trap geometries could reveal additional loss features and provide a more comprehensive understanding of the loss dynamics. Exploring the impact of these loss features on the stability and properties of dipolar quantum droplets and supersolids is a promising avenue for future research.

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Stats

The researchers produced Bose-Einstein condensates with more than 2 x 10^5 atoms.
The study identified six new loss features in erbium-166 at magnetic fields below 4 G.
The one-body lifetime (τ1) of the atoms in the optical dipole trap was determined to be 33(1) s.
The s-wave scattering length (as) at the chosen magnetic field for evaporation (1.4 G) is 73a0.
The evaporation efficiency (𝛾) achieved throughout the three stages of the optimized cooling sequence was 3.1(1).

Quotes

Key Insights Distilled From

Characterisation of three-body loss in ${}^{166}$Er and optimised production of large Bose-Einstein condensates

by Mila... at arxiv.org 11-25-2024

https://arxiv.org/pdf/2307.01245.pdf

$Characterisation of three-body loss in ${}^{166}$Er and optimised production of large Bose-Einstein condensates$

Deeper Inquiries

How might the understanding of these temperature-dependent loss features be applied to other elements or isotopes within the lanthanide series?

The observation of temperature-dependent three-body loss features in ${}^{166}$Er, potentially linked to resonant trimer states, offers valuable insights applicable to other lanthanide atoms like Dy, Tm, and Yb. These elements share similar electronic structures and strong dipole-dipole interactions, suggesting that analogous loss features might exist.
Here's how the understanding can be applied:

Predicting Loss Features: The resonant trimer model, if validated, could predict the positions and temperature dependencies of loss features in other lanthanides. This would require spectroscopic data on the molecular potentials and scattering properties of these atoms.
Optimizing Cooling and Trapping:  Knowledge of loss features is crucial for optimizing evaporative cooling and maximizing atom numbers in degenerate quantum gas experiments. By avoiding magnetic field regions with high three-body loss rates, one can enhance the efficiency of cooling and achieve larger atom numbers.
Exploring Few-Body Physics: The temperature dependence of these loss features provides a way to probe the underlying few-body physics governing ultracold collisions in lanthanide atoms. By systematically studying the loss rates as a function of temperature and magnetic field, one can gain insights into the nature of the resonant trimer states and their coupling to the scattering continuum.
However, it's important to note that the specific positions and characteristics of these loss features will depend on the detailed atomic and molecular properties of each element and isotope. Further experimental and theoretical investigations are needed to fully explore and exploit these phenomena in other lanthanide systems.

Could the presence of these loss features be exploited for the controlled manipulation or study of specific few-body quantum states?

Yes, the presence of these temperature-dependent loss features, attributed to resonant trimer states, opens up intriguing possibilities for manipulating and studying few-body quantum states in ultracold lanthanide gases. Here are some potential avenues:

State-Selective Loss: By tuning the magnetic field to a specific loss feature, one could selectively remove atoms in a particular three-body state. This could be used to prepare the system in a desired initial state for further experiments or to study the dynamics of few-body correlations.
Trimer Spectroscopy: The loss features themselves can be viewed as a form of trimer spectroscopy, providing information about the energies and lifetimes of these bound states. By carefully measuring the positions, widths, and temperature dependencies of the loss features, one can extract valuable information about the underlying three-body interactions.
Controlled Molecule Formation:  Three-body recombination, the process responsible for the loss features, can also lead to the formation of diatomic molecules. By controlling the magnetic field and temperature, one could potentially enhance molecule formation rates and study the properties of these molecules.
However, exploiting these loss features for controlled manipulation requires precise control over magnetic fields and temperatures, as well as a thorough understanding of the underlying three-body physics. Further experimental and theoretical efforts are needed to fully realize the potential of these features for manipulating and probing few-body quantum states.

If we consider the analogy of a crowded room emptying more slowly than expected, what other factors beyond individual interactions might contribute to the observed "stickiness" of the erbium atoms at specific energy levels?

The analogy of a crowded room emptying slowly is apt for describing the reduced loss rate between the resonant features. While individual two-body interactions would dictate a certain "exit rate," the collective behavior due to the dipolar interactions in erbium leads to unexpected "stickiness." Here are some factors contributing to this:

Dipolar Interactions and Correlations: Erbium atoms interact via long-range and anisotropic dipole-dipole forces. These interactions can lead to the formation of correlated many-body states, even in the thermal gas. These correlations can hinder the formation of the resonant trimer states, effectively reducing the three-body loss rate.
Quantum Statistics: Erbium atoms are bosons, and at ultracold temperatures, their quantum statistics become important.  The Pauli exclusion principle for bosons can influence the occupation of energy levels and affect the formation of trimer states.
Energy Dependence of Interactions: The strength and nature of the interatomic interactions can depend on the relative energy between the atoms. At specific energies corresponding to the resonant trimer states, the interactions are enhanced, leading to increased loss. However, away from these resonances, the interactions might be weaker, resulting in reduced loss rates.
Trapping Potential: The confining potential of the optical trap can also play a role. The trap geometry and anisotropy can influence the spatial distribution of the atoms and modify the effective strength of the interactions, thereby affecting the loss rate.
In essence, the "stickiness" arises from the interplay of dipolar interactions, quantum statistics, and the energy dependence of interactions. These factors can lead to collective behavior that modifies the simple picture of independent three-body collisions, resulting in the observed suppression of loss rates between the resonant features.