Quantum Q&A With 2025 Graduates

Last month, Columbia celebrated commencement for the class of 2025. Among those graduates are newly minted PhDs Valerie Hsieh, Morgan Thinel, and Ding Xu. Hsieh studied physics with Cory Dean, Thinel studied chemical physics with Abhay Pasupathy and Xiaoyang Zhu, and Xu studied chemistry with Milan Delor. 

Before they are off for their next adventures—Thinel is heading to Harvard, Xu to MIT, and Hsieh will be putting an undergraduate degree in German to use in Aachen—they shared some highlights from their graduate years at Columbia and advice for others. 

Where’s home, and why did you choose Columbia for graduate school?

Valerie Hsieh (VH): I've moved around a bit in the US but would call Lexington, Massachusetts home. I studied physics and German at the University of California, Berkeley. In 2018 and 2019, I was part of Columbia’s National Science Foundation Material Science and Engineering Research Center’s Research Experience for Undergraduates (REU) program as a visiting summer undergraduate in the Pasupathy and Dean labs. The REU was my first research experience, and I really credit my mentors, Matt Yankowitz and Shaowen Chen, for encouraging me to pursue graduate school and modeling a lot of the skills and characteristics that have shaped me as a researcher.

I appreciated that Columbia felt like a safe space to learn, grow, fail, and ask questions. I also particularly enjoyed the collaborative nature of the research—the sheer space constraints of doing research in New York City often mean that getting trained on lab equipment involves interacting with researchers from multiple labs. I liked how multidisciplinary collaboration was strongly encouraged.

Ultimately, I also chose Columbia for graduate school because I loved New York from my two summers in the city, and I was excited by the prospect of exploring every neighborhood, art gallery, Broadway show, cuisine, pop-up exhibit, museum, and opportunity that this glorious city has to offer. I have absolutely loved my time in New York—nothing will ever compare.

Morgan Thinel (MT): I am from Montréal, Canada, and studied chemistry at McGill University. I came to Columbia for graduate school for the people, the exciting and collaborative research environments, and the opportunity to live in New York. 

Ding Xu (DX):   My home is in China, and I studied at Wuhan University as an undergraduate. I chose Columbia because it is an excellent academic research facility in chemistry and materials science. 

What was the focus of your thesis?

MT: My main topic is the localization of electronic states in 2D materials. I used scanning tunneling microscopy and spectroscopy (STM/S) to investigate how electrons can become localized in thin metallic materials. This is important for two main reasons. The first is that electrons that are localized in space can be more easily manipulated. Control over electrons is crucial for developing quantum technologies related to the quantum properties of electronic states. The second reason is that localized electrons have stronger interactions with each other and with the surrounding lattice of atoms than freely moving electrons. Both these effects lead to quantum material properties such as superconductivity, lattice modulations called charge density waves, and other exotic phenomena, which again have applications in various quantum device technologies.

DX:   My thesis focused on using ultrafast optical techniques and nonlinear spectroscopy to study how a quasiparticle called a polariton moves and interacts in van der Waals semiconductors. The importance of my work lies in the key role of light–matter interactions in emerging van der Waals semiconductors. Understanding their behavior is essential for advancing next-generation optoelectronic and quantum photonic devices.

VH: My thesis was about using the atomic force microscope to probe graphene heterostructures. Much of the work on 2D materials—such as twisted graphene heterostructures—is done at cold, i.e. millikelvin, temperatures, which are far below the temperatures at which we live and operate. My work investigates the properties of these materials at room temperature and in ambient conditions, hopefully offering some insight into the correlation between room temperature properties and exotic phenomena that occur in quantum materials at low temperatures.

What’s been the highlight of your research experience at Columbia?

DX: One of the highlights of my research experience at Columbia was developing and applying ultrafast imaging techniques to directly visualize polariton propagation in van der Waals waveguides. It was incredibly rewarding to see light-like particles propagate in real-time measurements at femtosecond and nanometer scales.

VH: I don't have a single particular research memory, but rather a montage-like highlight reel that encompasses the joy of every research breakthrough I've had in grad school. Most of the moments involved running into the Dean lab postdoc office to show someone (anyone) an image of the scan frame, which showed an elusive moiré pattern on one of my samples. I am also particularly proud of the "Science as Art" award I received from the Materials Research Society at the spring 2023 conference in San Francisco, which shows an overlay of the Golden Gate Bridge over a background image of a scan I took with an atomic force microscope (AFM). 

MT: Working with amazing people and traveling for conferences around the US and the world, all while learning to do science that I never thought I would be able to understand, let alone make progress in.

What’s been the highlight of your time in New York?

VH: I have a lot of highlights, but I've particularly enjoyed the easy (and often quite affordable!) access to incredible performing arts and have been fortunate enough to see many Broadway shows, SNL tapings, film premieres, and ballet performances during my time in New York. In recent years, I've also found tremendous joy and wonderful friends through the vibrant running community in the city (shoutout Tour de Coffee run club!) and have loved exploring more of New York on foot. Running the New York City marathon will always be a special memory, and I look forward to returning to the city every November to experience the magic of touring the boroughs and celebrating New York with all of my friends.

MT: I met my fiancée in New York! 

DX: I’ve always enjoyed walking and exploring the city with my friends—whether it was checking out street markets, taking in the skyline from different neighborhoods, or just discovering new corners of the city.

Any words of advice for others?

MT: Remember that research requires patience and diligence, but also some luck! The best we can do as scientists is to remain curious and apply ourselves to our research without comparing ourselves to others. We can also always learn from others, even if they are working on a completely different science! I attribute a lot of what I've learned to good mentorship and discussions from my peers.

DX: Some of the most rewarding experiences come from stepping outside your comfort zone. Don’t be afraid to recognize your weaknesses or learn something completely new.

VH: Never approach a project as if it will fail, take the time to appreciate all the small victories, learn something from everyone you meet, and find joy in the mundane.

Scotch tape, in quantum research? Valerie explains the important role of this simple household item.