Laser Cooling Towards a Dipolar Quantum Gas of Erbium Atoms

Nathaniel Vilas - University of Cambridge
2018 - MPhil thesis

This thesis describes the design and construction of an apparatus meant to achieve degenerate quantum gases of erbium atoms. Erbium possesses a large magnetic dipole moment of 7µB, making it an ideal candidate for the study of long-range interactions in many-body quantum systems, and the present experiment aims to combine the study of long-range dipole-dipole interactions with quasi-uniform trap ping geometries to study, e.g., roton physics and supersolidity. The starting point is an atomic beam of Er atoms heated to 1200◦C, which we will collimate via trans verse laser cooling and decelerate with a Zeeman slower, home-built over the course of this work. Both processes take place on a broad, 30 MHz transition at 401 nm, allowing for efficient cooling and a compact Zeeman slower only 40 cm long. They are designed with several tunable degrees of freedom, which we can systematically optimize for maximum slow-atom flux at the experiment chamber. The next step is to load a magneto-optical trap (MOT) operating on a narrow, 200 kHz transition at 583 nm, which will enable the production of fully spin-polarized atom clouds at tem peratures as low as 5 µK. Throughout this work we have paid particular attention to the control and compensation of magnetic fields around the experiment cham ber, leaving the door open to future experiments requiring magnetic field tuning at near-milliGauss level. This level of control is particularly important for erbium, which along with its large magnetic moment also possesses many narrow, closely spaced Feshbach resonances. The results presented here represent a good starting point from which to work towards MOT and optical trap loading, followed by forced evaporation down to quantum degeneracy.