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A Bright Future in Dark Matter Research

Growing up, Riley Carpenter ’25 was endlessly curious. Between marathons of “How It’s Made” on the Science Channel and J.R.R. Tolkien’s “Silmarillion,” he always had a desire to know how complex things—from industrial machinery to Middle Earth mythologies—worked.

Carpenter knew he was interested in pursuing something in the world of STEM, but it wasn’t until his Introduction to Modern Physics class at ºÚÁϲ»´òìÈ that he found his calling: engineering physics—a unique degree in the College of Arts and Sciences that allows students to build their own emphasis. For Carpenter, that meant incorporating mechanical engineering, material science, and chemistry to widen the breadth and real-world applications of his physics degree.

“Physics has given me the most fundamental view on how things are created and the ability to break everything down to basic principles to reconstruct complicated systems,” he explains. “Because how things work often comes down to the materials being used, getting a wider exposure to these engineering fields has been so useful.”

At Santa Clara, he’s been able to put these diverse skills into practice, working for two years with physics professor Betty Young and her Stanford colleagues at the on a project . Through his contributions to this project, Carpenter’s already made waves in his field, winning a prestigious Barry Goldwater Scholarship in 2024 and a National Science Foundation honorable mention in 2025.

As he prepares to continue this dark matter research through a Ph.D. at Stanford University, Carpenter reflects on his personal growth, passion for music, and biggest research challenge..

Tell us a bit about your with Dr. Young. What makes dark matter so difficult to study?

Dark matter gets its name because when it moves through space, it’s practically invisible. In theory, dark matter may be detectable through collisions with atoms in a crystal, but even then, dark matter interactions are very tiny and usually get dwarfed by other things, so it’s a bit like looking for a needle in a haystack.

To get around that, our experiments work with superconductors cooled down to below the temperature of most outer space. While room temperature is 300 Kelvin and the lowest temperature limit of matter is 0 Kelvin, we use liquid helium to get to 4 Kelvin, and then at the SLAC National Lab, we have these fridges where we drop things down by another factor of 100 to get to about 40 milli-Kelvin to test our devices. At those low temperatures, we can minimize the vibrations of molecules, so we might be able to capture the tiny wiggles from dark matter.

Being able to confirm dark matter’s existence would be a major step towards refining our understanding of the fundamental physics of the universe. Based on that experimental result, theorists could start narrowing down which of their models are consistent with the dark matter mass range observed in detector data. Even without detection, this research leads to continual improvements in the quality and scalability of low-temperature sensors that have a whole host of potential applications beyond just dark matter searches.

With these low-temperature sensors, how do you design something that can tolerate those unforgiving temperatures while remaining sensitive enough to detect these tiny energy signatures?

You start with a silicon wafer, maybe half a millimeter thick, and you put very thin layers of metal on top. That film will be maybe 1/1000th the thickness of a strand of hair. Then you make a stencil to place over that film to blast away the exposed areas of metal, leaving behind the imprint from the stencil—these metallic patterns become the circuits for our nano-devices.

So, when we test these in the lab, if we see a change in the circuit response, we can say that something happened there, something hit the detector. Theoretically, that signal may originate from dark matter, though typically it comes from cosmic rays, which we’ll then use to calibrate our devices.

The fabrication process is the trickiest part because it’s very iterative, and that’s where things can go wrong. It’s honestly kind of similar to baking, where there are a lot of steps, and while you might use a generic recipe, your oven might be slightly different, and if you’re using a different type of tin to hold your brownies, you might get different results. So, after testing, I’ll bring our devices back to Santa Clara’s Center for Nanostructures where we have a scanning electron microscope that I use to identify any points of failure in our fabrication process.

Like you said, there’s a lot of trial and error in lab research. What was the biggest challenge you faced during this project?

During my first summer, I was brought onto a project where the early device yields were not very good. There were a lot of issues with reliability in the production process, and I was able to identify essentially a bug in the process that we were able to turn into a feature.

One of the chemicals we’d been using for one step was corrosive to some of our device materials. But then I realized that sometimes there are instances where you want to selectively remove material in a process called wet etching.

So, I was able to design a new procedure to use that chemical to do work for us instead of ruining our devices. Some of the grad students then were able to refine that procedure to produce devices that are now functioning and being tested up at SLAC.

Outside of this cool research, you’re also a member of ºÚÁϲ»´òìÈ’s Chamber Singers Choir. Can you tell us a little bit about how you’ve been able to pursue your love of music at Santa Clara?

In high school, I did a lot of choir and musical theater, and it’s been so rewarding to continue singing at ºÚÁϲ»´òìÈ. It can sometimes be a lot of hard work, but I really love the community and the opportunity to produce a unique sound at every performance and rehearsal.

I also feel like our director Scot Hanna-Weir also lets us perform impactful pieces that have important messages. One of my favorite performances was a piece called “Breathe in Hope” by Dale Trumbore that we sang my sophomore year. It was this call to action to recognize that there is the possibility of overcoming the challenges and suffering in today’s world. The song ends with the message that we each must work towards bringing about the future that we want to see.

ºÚÁϲ»´òìÈ really prides itself on providing a holistic, well-rounded education. How did coming to Santa Clara benefit your academic pursuits?

To me, Santa Clara seemed like a place where I could craft an education directed toward the interests I had. I knew I wouldn’t get thrown into a very generic program where every course you’d take is predetermined, and across my time at Santa Clara, I found that there was a lot of flexibility and personalization in the curriculum which allowed me to also pursue minors in mathematics and classics.

One of my favorite classes at ºÚÁϲ»´òìÈ was actually Professor Nicholas Lindberg’s course on Greek democracy where we ran a mock Athenian Assembly, and we saw it all fall apart as people became more corrupt. Being able to take a class so vastly different from sitting at a whiteboard all day has been a great part of my Santa Clara education.

Also, through that flexibility in my engineering physics degree, I’ve been able to customize my engineering physics major to my interests, and in the process, gain access to mentors from multiple departments and a lot of one-on-one support.

For example, had I been a traditional physics major, I probably wouldn’t have been able to take as many chemistry courses as I have. Because I was, Dr. Steven Suljak in the chemistry department became a great mentor for me. I actually sing with him in the Chamber Singers Choir on campus, and he was also the Office of Student Fellowships contact for the Goldwater Scholarship and the National Science Foundation fellowship program, so he was a huge help on my applications for those awards and graduate school.

Between getting an honorable mention from the National Science Foundation and receiving the Barry Goldwater Scholarship last year, do you have a proudest moment from your time at ºÚÁϲ»´òìÈ?

This past fall, I was able to present a lot of my results from the past two summers of work at the American Physical Society Conference for the far west region.

Giving that presentation and sharing my research with the broader community was really rewarding for me, and I got an undergraduate research award, which, again, was a huge moment of pride in what I had accomplished. I really appreciated that my work was acknowledged and it was great to bring that win back to ºÚÁϲ»´òìÈ.

How have you changed as a person at ºÚÁϲ»´òìÈ?

Again, through the nature of the coursework here, I’m a lot more well-rounded in terms of what I view as valuable to my education. Coming in, I was more focused on “STEM, STEM, STEM…” and by being here, I’ve really grown to appreciate how interconnected science, the humanities, the arts, and everything really is, and to excel in one, it is exceedingly valuable to study them all.

For example, I took a course on disability for my diversity requirement through the philosophy department. I found it to be a powerful course that gave me a lot of insight into different ways of thinking and the great variety of experiences for so many people. I’ve grown to apply that back even within physics, and better appreciate how important it is to foster a diverse group of individuals in science, because that’s how you can proliferate the most ideas from the most perspectives.

Do you have any advice for the incoming class of Broncos?

I would reassure them that you don’t need to have things figured out as a freshman. You can come to ºÚÁϲ»´òìÈ thinking you’re going to do one thing and realize that your path is very different—this university is a place where you can take a little bit of time that first year to determine what it is you want to pursue. If you let yourself explore, you can really do amazing things.

I’d also encourage students to really take advantage of the fact that this university is quite small and very undergraduate-focused and get in touch with their professors. That face time and direct mentorship can be so valuable. So, know that the door is open, but you still have to choose to walk through it.