Related Experiment Video
Updated: Jun 23, 2026
11:21
Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving
Published on: March 30, 2017
Extreme tunability of interactions in a 7Li Bose-Einstein condensate
S E Pollack1, D Dries, M Junker
1Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005, USA.
Physical Review Letters
|April 28, 2009
Summary
Researchers tuned the scattering length of lithium-7 Bose-Einstein condensates using Feshbach resonance. This allowed precise measurement of interactions across seven decades, revealing details of quantum behavior.
Area of Science:
- Atomic, Molecular, and Optical Physics
- Quantum Gases
- Condensed Matter Physics
Background:
- Bose-Einstein condensates (BECs) are quantum states of matter with unique properties.
- Controlling interactions in BECs is crucial for understanding quantum phenomena.
- Feshbach resonance is a powerful tool for tuning interatomic interactions.
Purpose of the Study:
- To precisely measure the scattering length (a) of a 7Li BEC.
- To explore interactions across a wide range, from attractive to repulsive.
- To investigate the influence of magnetic dipole interactions in BECs.
Main Methods:
- Utilized Feshbach resonance to tune the scattering length of 7Li atoms in the |F=1,mF=1> state.
- Measured the spatial extent of the trapped Bose-Einstein condensate.
- Analyzed data across a broad range of scattering lengths (7 decades).
Main Results:
- Successfully extracted the scattering length 'a' over seven decades.
- Determined 'a' down to 0.01 Bohr radii using a shallow Feshbach resonance zero crossing.
- Observed evidence of weak anisotropic magnetic dipole interactions by comparing different trap geometries.
Conclusions:
- Feshbach resonance provides a versatile method for controlling and measuring interactions in BECs.
- The study demonstrates the capability to probe interactions across an unprecedented range.
- Magnetic dipole interactions play a subtle but measurable role in BECs, dependent on trap geometry.
Related Concept Videos
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:27¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
01:08NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
01:12Fermi Level Dynamics
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...