Trapping the unseen: a new method to discover dark matter

In our recent podcast, we had the privilege of speaking with Dr. Lucia Hackermueller , an Associate Professor at the University of Nottingham, and Dr. Nathan Cooper, a postdoctoral researcher. Both of whom are at the forefront of groundbreaking experiments aimed at detecting dark matter.

Introducing Dr. Hackermueller and Nathan Cooper

Dr. Hackermueller provided an insightful overview of her career, beginning with her PhD at the University of Vienna under Nobel Prize winner Anton Zeilinger. “I worked with large molecules, trying to bring them into the gas phase and show interference,” she shared.

Her postdoctoral work in Immanuel Bloch’s group focused on ultra-cold atoms and degenerate quantum gases. Now an Associate Professor, she continues to explore fundamental quantum questions at the University of Nottingham.

Dr. Nathan Cooper, a postdoctoral researcher working alongside Lucia, specializes in experimental cold atoms. He detailed his journey, mentioning his Ph.D. and short postdoc at the University of Southampton before joining Nottingham nine years ago.

Special mention must also be made to Professor Clare Burrage from the School of Physics and Astronomy. Clare is another key member of the hunt for dark matter at Nottingham University and the central figure behind this idea from the theory side on which the practical work is based.

The challenge of detecting dark matter

As Lucia explained, dark matter “does not interact with light or electromagnetic fields, but it does interact with matter via gravity. Therefore, we struggle to detect it directly.” This inability to observe dark matter directly has led scientists to infer its existence through its gravitational effects on visible matter.

“In some ways, it would almost be better, at least for the perception of the general public, not to call it dark matter, but to call it anomalous additional gravitation, because that really is all that has been observed to date,” Nathan added.

Distinguishing dark matter from antimatter

A common point of confusion for many is the difference between dark matter and antimatter. Lucia clarified, “Anti-matter is much easier to understand than dark matter. It is the same as matter, just that it has the opposite charge. We can observe it, measure it, and even trap it. But dark matter remains a big question mark.”

The concept of domain walls

One of the intriguing aspects of Lucia and Nathan’s research involves domain walls. Lucia described them as regions where a scalar field changes value, forming boundaries that could potentially trap dark matter. “If we see a deflection, then we clearly know we have a domain wall. This would be a clear proof because, with a differential measurement, it cannot be anything else,” she explained.

Nathan emphasized the importance of stabilizing these domain walls for their experiments: “Because the effects we’re hoping to observe are incredibly tiny, we’ll need to repeat the experiment many times and take an average to see a systematic shift.”

The Role of Ultra-Cold Lithium Atoms

The team uses ultra-cold lithium atoms to detect these elusive domain walls. Nathan elaborated, “The lithium atoms are mainly just a very sensitive probe of their environment. Because they’re ultra-cold and isolated in a vacuum chamber, we can see extremely small perturbations.”

Lucia added that cooling the atoms allows precise measurements: “When the gas is cold, it does not spread as much, which helps us determine the position.”

Innovative use of 3D-printed vacuum chambers

A key component of their experiment is a specially designed 3D-printed vacuum chamber . Lucia highlighted the collaboration with theorists: “Our theory friends come up with this model and say the boundary conditions need to be like this, and that fixes the domain walls. We then print those boundary conditions with our 3D printer.”

Nathan also noted the practical advantages of this approach: “By using 3D printing, we can make the vacuum chamber exactly as theorists tell us, ensuring that the domain walls are pinned and fixed.”

The importance of differential measurements

Ensuring accuracy in their experiments involves performing differential measurements. Nathan explained, “The main thing is we’re going to perform a differential experiment. We change only one thing and look for a difference.”

Lucia elaborated on the process: “We can build two vacuum systems, one with spikes to pin the domain walls and one with just flat holes. We can then compare the deflection of the cold atom cloud in both setups to detect the presence of dark walls.”

Detecting dark matter would be revolutionary

The potential discovery of dark matter would be monumental. Lucia remarked, “If we see a deflection, then we know we have a domain wall. This would be clear proof because, with a differential measurement, it cannot be anything else.”

Nathan added, “In terms of sheer intellectual curiosity, it’s a big deal. By understanding this bit of physics, we understand the rest of physics better, which has real-world consequences.”

While the practical applications of dark matter may not be immediately apparent, the knowledge gained from such discoveries can significantly advance our understanding of the universe. Lucia succinctly said, “We will be able to know much more about the universe and the things that we can observe out there.”

Dr. Lucia Hackermueller and Nathan Cooper’s work represents a crucial step in the ongoing quest to unravel the mysteries of dark matter. Their innovative use of ultra-cold atoms, 3D-printed vacuum chambers, and differential measurements showcases the cutting-edge research at the University of Nottingham.

As they continue their experiments, the scientific community eagerly awaits the potential breakthroughs that could fundamentally change our understanding of the universe. You can keep abreast of their work on Nottingham University’s website.