The discovery 101 years ago of superconductivity—a quality in metals and ceramics that allows electricity to flow without loss of energy at low temperatures—opened the doors to a host of practical applications including electronic devices, high-efficiency transportation systems, electrical generators and medical magnetic resonance imaging (MRI).
To observe the centennial of this landmark discovery, Associate Professor Thomas Gredig and Professor Andreas Bill of the California State University, Long Beach (CSULB) Physics and Astronomy Department co-organized a workshop on “Trends on Nanoscale Superconductivity and Magnetism” from June 29 to July 1, 2011 in Cali, Colombia. The proceedings of the workshop appear this October in issue 7, vol. 25 of the Journal of Superconductivity and Novel Magnetism.
Other organizers and presenters included Axel Hoffmann from Argonne National Labs and conference chair Maria Elena Gomez from Universidad del Valle, Cali. They, along with guest speakers from the United States, South America and Europe, discussed their latest research on superconducting thin films and magnetism.
Travel is vital for establishing scientific collaborations, exchange of ideas, and name recognition. In the last couple of years, reduced state funding to CSULB has severely limited academic travel and conference opportunities for faculty as well as students, so Gredig was able to receive an external $25,000 National Science Foundation (NSF) grant that supported travel for 10 U.S. graduate and post-doctoral physics students, including two from CSULB, to present their own research and learn about research done in South America.
“In addition, the event provided a platform for discussion of present challenges, both theoretical and experimental in the fields of nanoscaled materials, and a particular focus on developing future pathways and directions,” Gredig said.
Attendees also explored research directions not currently pursued in the United States and identified ways to promote exchanging knowledge and expertise among research groups of different nations; for example between the United States and Colombia. “It also broadened the horizon of separated communities both working on advanced nanomaterials, but publishing in different outlets,” Gredig added.
In a post-conference survey, the NSF-sponsored U.S. participants expressed an enhanced positive attitude towards physics research in South America, particularly Colombia and booming Brazil, and expected to begin research collaborations between the United States and South America. This may be an innovative approach to discover novel magnetic and superconducting materials for applications, Gredig and Bill said.
A Ph.D. student from Universidad del Valle visited Bill’s group during a week last October to speak with Physics and Astronomy Department faculty about his work, and another student who attended the conference expressed interest in joining CSULB’s physics master’s program in 2013.
While in Cali, Gredig and CSULB student Jorge Guerra spoke on “Magnetic Response in Low-Dimensional Organic Semiconductors.”
“My role at the conference was primarily to help Dr. Gredig answer questions concerning his research and to learn a bit more about the interesting field of superconductors, which was discovered 100 years ago this year; and magnetism, which has been found in certain superconducting materials under the right circumstances,” Guerra said.
Their research is funded by Gredig’s NSF CAREER grant, one of the agency’s top awards for exceptional scientists early in their careers. Guerra completed his master’s in physics at CSULB this summer and is in the process of applying to Ph.D. programs in Europe.
“The research Dr. Gredig presented on behalf of our group concerns the magnetic and electrical properties of a blue industrial dye called phthalocyanine, which is interesting from a physics perspective for a number of reasons,” Guerra said. “To begin with, it’s an organic material. This means that it is generally more complex and that its electronic and magnetic properties are less well understood than crystals made up of a couple of different elements. It can also be made into extremely thin films 1,000 to 10,000 times thinner than the diameter of a human hair, made up of tightly packed grains whose shape can be controlled during the film-making process. Lastly, in terms of our interests, the molecule itself can be made to have different metallic elements at its center.
“The work presented in Cali was regarding the interesting magnetic effects we have measured in thin films of the iron-centered version of this molecule,” he continued. “The fact that iron has magnetic properties is fairly common knowledge, so it is not surprising to measure magnetic effects in these films. It turns out, however, that the magnetic effects in these films are significantly different from those in pure iron, and our ability to control the size of the grains in the films gives us some control over these magnetic properties. We attribute this to the formation of iron chains within the grains, with longer chains amplifying a particular effect and shorter grains reducing it.”
Student Thomas Baker and Bill discussed “Classical Mechanics Analogies in Magnetic Thin Films,” and Bill spoke on “Properties of Magnetic-Superconducting Proximity Systems.” Research by Bill and his students is funded by the NSF and by the Army Research Laboratory. In addition, Baker received a CSULB Graduate Research Fellowship and a Phillip J. Ord Scholarship, and he won first place in the 2012 CSU-wide Student Research Competition in the Physical Sciences and Mathematics category.
A basic physics concept is oscillatory (periodic) motion—for example, the swinging of a pendulum—but the mathematics to describe this motion often are approximations, said Baker, who completed his master’s in physics at CSULB this spring and began his Ph.D. in physics at UC Irvine this fall.
“We found a solution which is exact for a pendulum and a similar system consisting of a pierced bead threaded onto a wire hoop that exhibits curious behavior when we spin the hoop, like a coin on a table. That is, the bead does not remain at the bottom of the hoop, but rises to a certain height if we spin the hoop fast enough,” he said. “Our interest in the problem was that the mathematics are identical to that of a magnetic thin film and we will apply what we have learned from these problems to magnetism.”
In Bill’s presentation, he noted that when a magnetic material is in close proximity to a superconductor, as is the case in a thin films multilayer, properties of both materials are drastically modified near the interface.
“Electrons from the superconductor form Cooper pairs, but in most cases these cannot penetrate deeply into the magnetic material without being broken (a few nanometers at most). It was recently discovered, however, that under certain circumstances Cooper pairs can survive in the magnetic material,” he said, adding that his group is investigating conditions under which this state can occur. They are presently preparing their findings in a set of publications. “Once harnessed, this phenomenon can be utilized to develop novel components for future electronic devices.”
The opportunity to present their research before an international audience and see it published in major research journals benefits CSULB students and is one reason why the NSF has rated the campus among the top master’s universities in the number of graduates who go on to earn doctorates in science and engineering.
“Dr. Bill and Dr. Gredig, along with the rest of the committee, put on a wonderful conference,” Baker said. “I know everyone attending had a great time learning physics and meeting other professionals. I am definitely lucky to be in the department studying here.”