Month: January 2024

AS AN UNDERGRADUATE at UC San Diego, I knew I wanted to work in science or engineering but I wasn’t sure what I specifically wanted to do “when I grew up.” That’s why I majored in physics–it’s versatile.

After earning a PhD in physics at UC Santa Barbara, I worked for years as an academic researcher at Lawrence Berkeley National Lab (LBNL). I later veered off this career path, merging my passions for science and writing. On the surface, my physics degrees may seem unnecessary for a science journalist, given that I mostly write about medical research. But my physics training is integral to how I research, interview, and write. So, I was intrigued to speak with several Berkeley Physics alumni doing non-academic jobs to see how they apply their physics degrees.

“Physics education and training will serve you well in whatever profession you want to pursue.”

Marc Peters is an intellectual property attorney at Turner Boyd LLP. He helps clients resolve disputes related to technology, including those involving patents, trade secrets, and copyrights.

According to Peters, “thinking like a physicist” means approaching issues with the right level of abstraction, which helps determine what matters, what does not, and what is “good enough.” It also requires the curiosity to always ask “why.” These are key skills for a successful litigator.

“I was fortunate to have Professor Marjorie Shapiro as my advisor and to work with the CDF group at LBNL. They taught me how to break down any problem into solvable chunks and how to work with a group of really smart people, which I am fortunate to still do,” says Peters. “And my electronics, semiconductor, programming, and teaching experience helps me understand my clients’ technology and helps me communicate it to non-technical judges and juries.”

Peters offers some advice to current students: “Physics education and training will serve you well in whatever profession you want to pursue. You’ll learn how to learn—and that is a huge advantage in any career, inside or outside of science.”

Erika Isomura is currently a fifth-grade elementary school teacher at the Hayward Unified School District. Although she initially thought she would teach high school physics, she’s spent the last 25 years teaching all grades between second and sixth grade.

When discussing her work, she sounds like an experimental researcher. “In teaching, you don’t know in advance how things are going to turn out. So, you think about the variables, potential outcomes, and desired outcomes. And then you try things out with the kids, reflect upon what you learned, refine, and use those modifications the next day,” says Isomura. “I tease my kids that I’m a scientist experimenting on them.” She also applies this experimental approach to teaching yoga to kids.

Isomura credits her methodical planning skills to her Berkeley Physics training. Teachers need to be able to identify an end goal, as well as break that goal into manageable chunks that help students feel successful, she says.

“My work has also benefited from the classes I took at Cal. I often tell my kids about Professor Clarke, my quantum mechanics professor. His tests were open. He said it was more important that you knew how to apply the concepts than memorize or just blindly derive things. And I’ve taken that to heart,” Isomura says. “I mostly use application-level exams, rather than asking students to memorize and regurgitate something; I think that’s benefited my students.”

David Brahm recently retired as a financial portfolio manager at Geode Capital Management. As a quantitative analyst, he typically spent his days programming mathematical financial models—using databases of financial statements from several thousand companies—that aimed to maximize stock returns and minimize risk. As he describes this big data optimization problem, he is clearly still thinking like a physicist.

“To a physicist, a stock portfolio is a vector of expected returns. And every stock has some volatility, but there are also strong correlations; for example, within the airline industry. So, risk is basically a covariance matrix. And we can put these together to solve a straightforward quadratic optimization problem, where we maximize the return and minimize the risk,” explains Brahm. “Like a physicist, we make simple, useful models. However, these models can fail during an extreme event like the pandemic.”

Jeffrey Hunt is a Senior Technical Fellow at the Boeing Company. He is essentially a professor in an international company. He publishes, gets patents, gives talks, and interfaces between the technical and managerial sides of the company—always pushing the forefronts of their technology.

According to Hunt, Berkeley Physics training contributed to his success in industry. “I learned how to see the big picture, be creative, and solve problems,” he says. “My training was also very broad—optics, electronics, computer algorithms, and more—which has enabled me to reinvent myself, move around, and advance at Boeing. A physics degree is the liberal arts degree for the new millennium.”

Hunt also appreciates that his Berkeley Physics group included students and postdocs from around the world, preparing him for global collaborations.

Nasreen Gazala Chopra is the Vice President of Systems Engineering and Sustainability at Applied Materials. She spends most of her time in meetings, where she relies on the fundamentals that she learned at Berkeley Physics to successfully understand and engage in technical discussions.

“Physics also helped me think more clearly and become a stronger problem solver,” she says. “Its generality helped me get an entry ticket to jobs. And I get a lot of respect as a capable person because physics is challenging.”

Since getting her PhD in physics at Berkeley, Chopra has worked in various roles, industries, and companies, including a Silicon Valley startup, Apple, the solar industry, and the semiconductor industry. She is now excited to share this industry experience as a new member of Berkeley’s College of Letters and Science Advisory Board.

“I’m looking forward to brainstorming with my fellow board members on how we can enrich the students’ curricula and experiences,” she says. “Berkeley has a reputation for being a leader in change. I’m interested in having a frontline seat to see how that’s being implemented.”

This is a reposting of my magazine feature courtesy of UC Berkeley’s 2023 Berkeley Physics Magazine.

BERKELEY PHYSICS FACULTY ARE DRIVEN to understand the fundamental physics of materials. Theorists hypothesize the existence of new forms of matter and behaviors, and their experimentalist colleagues develop novel materials and tools to observe these exotic properties.

“We can now control parameters to systematically study how a material goes from one quantum phase to another quantum phase,” says Berkeley Physics Professor Feng Wang, the Williams H. McAdams Chair in Physics. “Instead of solving equations in a computer, we can design model systems in our lab to test and understand the underlying mechanisms of phase formation and the properties of different phases.”

The community of condensed matter physicists researching exotic materials includes experimentalists Mike Crommie, Alessandra Lanzara, and Wang, who are physics professors at Berkeley and senior faculty scientists at Lawrence Berkeley National Lab.  

Although understanding the fundamental physics is what most excites Berkeley physicists, they also expect exotic materials to lead to important applications.

“People talk about using these new materials for future quantum technology—either in quantum sensing or quantum computation—where switching is done by alternating between quantum states,” says Wang. “People are also exploring whether they can replace silicon, allowing transistors and electronics to become even more miniaturized.”

BUILDING EXOTIC 2D MATERIALS

How to create exotic 2D materials is not obvious, but Crommie offers some guidance. “In most conventional materials, the periodicity—the distance between the atoms and how they’re arranged in the lattice—determines the behavior. Electron-electron interactions and topology don’t play a big role,” says Crommie. “We make so-called exotic 2D materials by modifying these properties using techniques developed in recent years, using three general approaches.”

In the first approach, the researchers stack and rotate atomically-thin layers of different materials to create what is called a 2D moiré superlattice. Strong covalent bonds provide in-plane stability, whereas relatively weak van der Waals forces hold the layers together. And a small mismatch in the spacing of the atoms between the layers produces an interference pattern—like when you put two screens together and rotate one—thus creating a new superlattice periodicity.

“Moiré superlattices allow us to engineer new lattices for electrons and to control their correlation behavior,” says Wang. “We’re building quantum materials by design with an unprecedented control that doesn’t exist in nature.”

In the second approach, the scientists induce exotic behavior from conventional 2D materials by very carefully controlling the electron density and screening environment.

“For example, if we take a single layer of a transition metal dichalcogenide (TMD) and put electrons in it at a very low density, then the electrons crystallize into a pattern called a Wigner crystal,” says Crommie. “That’s a very exotic behavior where the electrons freeze like ice into a new crystalline phase, because the potential energy dominates over the kinetic energy. Wigner crystals were predicted almost 90 years ago, but we can image them now in new 2D materials.”

In the third approach, they create novel excitonic states in topological insulators, materials that behave like an insulator in their interior but conduct electricity along their surfaces.

“On the surface of a topological insulator, it’s like there are two freeways for electrons. Electrons with one spin move in one direction, and electrons with the other spin move in the opposite direction,” says Lanzara, the Charles Kittel Chair in Physics. “Our goal is to use optical pulses and leverage the topology and bulk/surface properties of these materials to engineer new quasiparticles.

“Having access to higher resolution tools and new ways of probing materials is how we make new discoveries. It’s a must if you want to lead the way to new science.”

DEVELOPING NOVEL TOOLS

To build and investigate a diverse range of exotic 2D materials, Berkeley physicists are pioneering new techniques. “Having access to higher resolution tools and new ways of probing materials is how we make new discoveries. It’s a must if you want to lead the way to new science,” Lanzara says.

These experimentalists have favorite tools; for example, Wang specializes in studying how light interacts with materials.

“We use optical photons from near microwave to UV,” says Wang. “The combination of optical modalities depends on the material and the specific questions we’re trying to answer.”

Optical spectroscopy is Wang’s primary technique. But his group also uses scanning tunneling microscopy (STM), including a novel non-invasive spectroscopy technique he developed with Berkeley Physics Professors Alex Zettl and Michael Crommie.

Together they built a moiré superlattice from single layers of tungsten diselenide and tungsten disulfide and then added a spacer layer of boron nitride capped by a top layer of graphene. The graphene layer enabled them to sense a delicate crystal of electrons within the TMD moiré structure without destroying it with the STM tip. The spacer layer prevented electrical shorting and permitted independent doping for the TMD and graphene layers.

“We made the first real-space images of 2D Wigner crystals in our moiré superlattice by actually imaging a lattice formed by electrons. We were able to see the correlated ground state and interesting excited state properties,” Wang says.

This approach could also be used to image electron lattices in other materials, rather than relying on a “magic angle” between the layers to control the correlations. “Our TMD moiré superlattices exist even at zero twist angle due to the lattice mismatch, and the correlation effects remain strong,” says Wang.

Berkeley physicists are also directly measuring electrons and spin in momentum space using novel spin-, time-, and angle-resolved photoemission spectroscopy pioneered by Lanzara and her coworkers. In this technique, a material is irradiated with a beam of ultrafast photons and the spin, speed, and direction of the ejected photoelectrons are measured with incredible sensitivity to figure out what’s happening inside the material. Lanzara’s latest instrument, named the momentum nanoscope, can also look at real space.

Lanzara recently used her state-of-the-art system on the topological insulator bismuth telluride to search for novel types of excitons, which are charge-neutral quasiparticles created when light is absorbed in a semiconductor. Her team discovered and characterized the first spatially indirect topological exciton state. “The electron trapped on the surface is coupled to a hole confined in the bulk, generating a long-lasting spatially-separated exciton that retains the special spin properties inherent to topological states,” she says.

One potential application of exotic materials is sustainable electronics that stays cool. “Your cell phone and computer heat up because charges bounce into each other as they move,” explains Lanzara. “Some of these new 2D and topological materials allow information to be transported instead through spin, minimizing interactions and eliminating heating issues. Moreover, they can be combined as Lego-like blocks, enabling easy assembly of materials on demand that are reusable and recyclable.”

Just think, you might have an exotic 2D material in your pocket someday.

This is a reposting of my magazine feature, courtesy of UC Berkeley’s 2023 Berkeley Physics Magazine.