By: Lisa R. Weidman
When you enter Dr. Dan Litvin’s office, you may think that you just stepped into a Toys “R” Us by all the models and toys that are on display. In reality, these are all teaching aids that he uses in his physics classroom.
Litvin is a Distinguished Professor of Physics at Penn State Berks who has received sixteen years of research grant support from the National Science Foundation. His current research interests include symmetry-based predictions of physical properties of crystals and group theoretical applications in physics and crystallography. In other words, he looks at the symmetry of materials and asks what it means about the properties of materials.
From a practical standpoint, Litvin can analyze the symmetry from certain crystals and determine that the electrical properties will be the same in different directions, or that there will be relationships between electrical and magnetic properties because of the symmetry of the crystal.
According to Litvin, one of the most important goals in the application of technical physics is to determine how to manipulate properties of materials via the electrical properties. For example, people save information on CDs because of the magnetic properties of the material. They can manipulate these magnetic properties with other magnetic properties–that’s how you write to a CD. But it would be much easier if they could use electrical properties. No one has perfected a method to accomplish that as of yet.
Litvin adds that he is a theoretician, who is somewhat removed from practical applications. He could advise an experimental scientist who is looking for specific properties of a material to look for a certain symmetry, but as far as which properties and which materials, he does not know.
An example of this type collaboration is when Litvin recently joined forces with Venkatraman Gopalan, Professor of Materials Science and Engineering at Penn State University Park campus, on the discovery of a new type of symmetry called “rotation-reversal symmetry,” described as “a new way of understanding the structure of proteins, polymers, minerals, and engineered materials that will greatly expand the possibilities for discovering or designing materials with desired properties.”
Before the publication of Litvin’s and Gopalan’s paper in the journal Nature-Materials, scientists and engineers had four different types of symmetries to use as tools for understanding the structures of materials whose building blocks are arranged in fairly regular patterns. Three types of symmetries had been known for thousands of years–rotation, rotation inversion, and translation–and a fourth type–called time reversal–had been discovered about sixty years ago.
Now, researchers at Penn State have added a new, fifth type, called rotation reversal. As a result, the number of known ways in which the components of such crystalline materials can be combined in symmetrical ways has multiplied from no more than 1,651 before to more than 17,800.
“We mathematically combined the new rotation-reversal symmetry with the previous four symmetries and now we know that symmetrical groups can form in crystalline materials in a much larger number of ways,” states Litvin.
“Rotation reversal is an absolutely new approach that is different in that it acts on a static component of the material’s structure, not on the whole structure all at once,” Litvin explains. “It is important to look at symmetries in materials because symmetry dictates all natural laws in our physical universe.”
According to Litvin, the most simple type of symmetry–rotation symmetry–is obvious, for example, when a square shape is rotated around its center point. The square shows its symmetrical character by looking exactly the same at four points during the rotation: at 90 degrees, 180 degrees, 270 degrees, and 360 degrees. The new rotation-reversal symmetry is obvious, as well, if you know where to look.
At any one time, Litvin is involved in several different research projects. For the last twenty-five years, he has been working with the same two scientists from the Institute of Physics in the Czech Academy of Sciences on a variety of studies. Currently their research focuses on using symmetry to predict the structure of so-called domain walls.
In addition to his research, one of Litvin’s main goals is to provide information to the scientific community. For the last thirty years, he has been working on research in the area of magnetic symmetry. He notes that no one has set out the characteristics of these symmetries and presented them in a manner that can be used as a reference to other scientists’ work, so he took it upon himself to put together a 11,000-page reference book of this information as a service to the scientific community. He also published a web site with this information.
In addition, he is very active in several professional organizations, including the International Union of Crystallography.
Throughout his academic career, Litvin has produced 111 publications and journals–20 with undergraduate students at Penn State Berks.
“When I work with students, I give them a project that will lead to a publication,” states Litvin. “It is not busy work: It is a project with scientific interest. It is amazing how capable the undergraduate students are. I have found some fantastic students here at Penn State Berks.”
When asked what led him to the field of physics, Litvin explained that he originally wanted to be a medical doctor. He jokes that when the Russians beat the United States by being the first to send a satellite around the earth, his career focus changed.
“Sputnik mania back in the late 1950s caused me to decide to stand up and be counted and come to the aid of my country: I decided to become a scientist.”
After a year of college in Chicago, Litvin transferred to the Israel Institute of Technology in Haifa, Israel. Since he did not know the Hebrew language, he went from being a straight “A” student to barely passing.
“The world is a very interesting place and I got to do things I never would have done if I would have stayed here. I married a beautiful girl from the Middle East and our kids were born there.”
Litvin taught himself to read and write the language, completed his doctorate, and then completed post-docs in Canada and Washington D.C. He then came to Penn State Berks, where he has been teaching and conducting research for the last thirty-three years.
“I’m not thinking about retirement. I’m having fun with the students: I enjoy being around them. I can’t stand people my own age,” he adds jokingly.
“There’s a Hebrew word ‘balagan,’ which means chaos–that’s how I picture my life. I like toys–I use them to demonstrate physics principles.”
Litvin ends the interview by using his Sesame Street Bert doll on a swing to demonstrate the transference of mechanical energy. What better way to learn about physics!