Simple Magneto-Optical and Magnetic Traps for Dysprosium

TL;DR

This work demonstrates a simple, robust dysprosium magneto-optical trap that loads directly from a thermal beam using a single diode-laser system, with the magnetic quadrupole field serving both the MOT and magnetic trapping. The authors characterize loading time scales, determine the capturable fraction of atoms, and achieve a total magnetically trapped population of $N_t=1.14\times10^{5}$ atoms at $T=28~\mu\text{K}$, with $85\%$ in dark states. The study shows that a minimal, diode-laser–based approach can yield substantial trapped populations suitable for exploring dipolar interactions in Dy, offering a simpler platform for future quantum-gas experiments. The combined measurements of loading dynamics, speed distributions, and trap populations establish a practical pathway toward accessible Dy experiments that leverage strong magnetic dipole–dipole interactions for many-body physics.

Abstract

Dysprosium (Dy) is the most magnetic element on the periodic table, making it excellent for studying dipolar atom-atom interactions. We report on a simple Dy MOT that captures atoms directly from the thermal beam using a single diode-laser system to generate the light. Additionally, the atoms are magnetically confined by the quadrupole magnetic field that also facilitates the MOT. The MOT loading time is $τ_\text{b} = 26~\text{ms}$. Atoms can decay to a dark state that is magnetically trapped. The time constant for loading into this magnetic trap is $τ_\text{d} = 410~\text{ms}$. The total magnetically trapped population is $1.14\times10^{5}$ atoms, with $85\%$ residing in the dark states. The magnetically trapped atoms have a temperature of $28~μ\text{K}$, significantly below the Doppler limit. This population fulfills the requirements for a range of future experiments.

Figures (11)

• Figure 1: Overview of the Dy MOT and magnetic trap setup, showing how the effusion cell, vacuum chamber, quadrupole coils and three laser beams (the third is coming out of the page) are combined to form the Dy MOT. The quadrupole coil also provides the magnetic field for magnetic trapping.
• Figure 2: Schematic of the laser system, used to form and analyze the Dy MOT, showing the distribution of the three laser beams. Also shown is the feedback loop for the cavity locking mechanism and imaging light power control
• Figure 3: CAD schematic of the vacuum chamber, showing the effusion cell in orange on the right, the science chamber in black on the left, separated by the differential pumping tube shown in blue
• Figure 4: Cross-section of one quadrupole coil, showing the main dimensions and how the square hollow conductor is used for water cooling.
• Figure 5: Electrical circuit used to switch the quadrupole coils, showing the IGBT controller chip in the center and electrically isolating the circuit using an opto-coupler on the left. Also shown is the TVS diode on the right that prohibits voltage spikes.