Published August 05, 2021 by Angela McKenzie '23

Physics Students and Professor Make Strides in Solid State Research at Bowdoin and Beyond

Current solid state research being conducted by department chair, Madeleine Msall, and her student researchers, Kieran Enzian ‘22 and Lorenzo Hess ‘23, has the potential to advance the research efforts of faculty and students in and beyond Bowdoin.
Msall Hess and Enzian Performing Hall Measurements
From left to right: Madeleine Msall, Kieran Enzian, Lorenzo Hess

 A year and a half after the COVID-19 pandemic forced her research efforts to shut down, Msall, with the help of Enzian and Hess, has returned to the lab to continue her study of surface acoustic waves (SAWs). 

Since the lab was completely shut down in March 2020, this summer is dedicated to restarting the equipment and building up capacity for future student research” Msall notes. 

Msall first began working with SAWs as a graduate student at the University of Illinois at Urbana-Champaign. Since then, she has hired Bowdoin students in her lab to introduce them to the process of academic research in the sciences.

This summer, Msall is working with Hess and Enzian to develop the framework for future research efforts at the college. 

“This work [developing lab infrastructure] is not the most glamorous part of research, but it’s a necessary and often engaging level of problem solving and testing that supports overall research capacity at the college.” 

One of the major projects within the group's research is the integration and test of a new metal deposition system. Hess, a rising junior, has worked closely with the new machinery this summer. Using Hall effect measurements, Hess has been able to characterize different aspects of  the machine’s deposition abilities. 

“The idea is that we'll make depositions at various heights just by lifting the stand closer to the sputterer and then running Hall effect measurements on those bars. Then if we get good data for the Hall voltage in the bar, we can calculate the thickness and figure out the thickness as a function of height” Hess explained in an interview.

Msall notes that this work is critical in not only her own research but also in the future lab work of advanced students at the college.

“Once the bugs are out, students who perform the famous Hall experiment in our advanced lab (PHYS3010) will be able to make their own Hall bars.”

The other important piece of the group’s work is the development of COMSOL software to model how the solids will respond when subjected to different acoustic and electric signals. Enzian, a senior physics major at the college, has spent his summer investigating this portion of Msall’s research.

According to Enzian, “the COMSOL models help determine how the SAWs will move through different surface patterns on the solids. It’s a lot of building the geometry of the devices and then applying the different types of physics and boundary conditions.”

Enzian's COMSOL model of an Infinite Periodic IDT
Enzian's COMSOL model of an Infinite Periodic IDT
Hess's 100 Angstrom Copper Deposition
Hess's 100 Angstrom Copper Deposition

From Bowdoin to Berlin 

Since her last sabbatical in 2017, Msall has collaborated with researchers at the Paul Drude Institute based out of Berlin, Germany. Her work with their Control of Elementary Excitations by Acoustic Fields group has shaped the trajectory of her future research. 

“Paulo Santos, the group leader, introduced me to the power of shaping acoustic transducers, the devices that generate and detect our surface waves, in order to focus them on low dimensional electron systems. My work has been to incorporate my expertise on phonon focusing, the tendency of wave energy to flow along preferred directions in crystals, into the transducer design."

The Berlin group is investigating how SAWs can be used to manipulate electron systems of three dimensional potential wells called quantum dots. Msall notes that such manipulation of individual electrons is an important piece in understanding how quantum computing works.  

One important project from the Santos group is working to make a SAW switch for quantum computing applications.”

Msall emphasized that the work Enzian and Hess are performing this summer is an important part in the advancement of her research with the group. Looking towards her next sabbatical, Msall hopes to return to Berlin with data collected from the Bowdoin lab. 

“Down the line, the deposition system will be used in conjunction with our fine line photolithography equipment to produce MHz acoustic wave generators for my research. The COMSOL software helps predict the type of film patterns that will most effectively generate the acoustic waves used to interact with electron systems.”

Although there is still substantial research to be done before Msall returns to Germany, she is grateful for the work her group has been able to accomplish this summer. 

“My greatest success right now is just showing up and making incremental progress” Msall acknowledges. “It’s super helpful to have strong students who are enthusiastic about the work who help me keep my eye on the big picture.”